The Barrier Depths Distortion is the final bonus dungeon added into Souzinengi V. As a result, it wasn't available to english speaking players until now and, thus, there's effectively no english info on the dungeon available. It serves as the game's true final challenge and, just like the Deepest Depths, is rather long and arduous. Fully clearing it will take just about everything you've learned on your journey so far.

Note: Thank you to ZeldaFan024 for providing the exact rooms each enemy can be found in. You can check out their guide on that here: https://steamproxy.com/sharedfiles/filedetails/?id=3038934024

To unlock the Barrier Distortion, you need to defeat the Resentment Incident, the final boss of Lingering Summer Heat, and also defeat Chronos at the deepest point of the Deepest Depths of Resentment. Once you're ready, just return to the shrine and accept the quest "Final Quest: Those Whose Path was Blocked," and the stairs leaving the shrine will now take you into the Barrier Distortion instead of returning you to the overworld.

1. Forest of Magic - A-B
   
   
2. Garden of the Sun - C
   
   
3. Genbu Ravine - D-F
   
   
4. Great Library - G-I
   
   
5. Bhavaagra - J-K
   
   
6. Lakebed Temple - L-O
   
   
7. Great Temple - P-Q
   
   
8. Forest of Magic (Purple) - R
   
   
9. Hakurei Shrine - S
   

NOTE! Do not attempt this dungeon until reaching at least level 80. Make sure you've synthesized either a Super Ajan or Platinum Ore/Barrier Stone tier weapon for every character along with a plethora of high rank defensive accessories.

Thankfully, progress through the Barrier Distortion is relatively straightforward until you reach the Lakebed Temple section. Just make sure you take the center door at the start of the Genbu Ravine section in room D.

As a note, once you reach the Great Library section (in room H after the transitional room G), enemy encounters will get more dangerous. I recommend being level 85 before trying to fight too much from this point.

Right before reaching the Lakebed Temple section, at the end of room K, is a one time use healing circle. Just walk around it if you don't need it and keep it in mind for later.

Once you start the Lakebed Temple section in room L, you'll find your path forward blocked by a green barrier, just like in the original Lakebed Temple.

Instead, start by taking the path on the right and loop around the back of the room to reach the door to room M on the left.

Once in room M, follow the maze to the end and step on the first switch.

Now, return to the start of room L. This time, take the path on the left, passing by the barrier, to reach the door to room N on the right.

Once in room N, follow the maze to the end and step on the second switch.

Upon returning to room L, you'll find that the barrier has vanished, opening the path to room O.

Room O is simpler, even if it take a bit of spiraling around, but it's merely a breather for room P, the Great Temple section.

Room P is a confusing screen-loop maze in which you need to find your way to the opposite side of the starting platform. Without a minimap, this is a nightmare, but if you're not interested in the loot (or you've already opened the chests), just follow this path to head straight to the end.

1. Head left from the entrance and down the stairs.
   
   
2. Head through the underpass.
   
   
3. Take the path on the right and move straight ahead, ignoring both underpasses.
   
   
4. Pass through either of the underpasses on the left.
   
   
5. Head up the stairs and into room O.
   

Fun Fact! The two statues at the start of the maze actually don't have collision. You can use this for cutting into a different part of the maze faster, but neither side of the statues are on the exit path.

Room O just has a teleporter and two chests. Ignore the chest on the right and take a breather before taking the teleporter. Every single encounter in the next room is incredibly powerful and WILL party wipe you very fast if you're not specifically prepared to deal with it. You'll need to make a mad dash for the end of the room, avoiding everything. As soon as you're prepared, step on the teleporter to room R, the purple Forest of Magic section.

Once you make it to the end of the room, flip the switch to activate the shortcut teleporter.

The passageway to your right will then lead to the boss room in the Hakurei Shrine section, so use the healing circle at the start of the room, and take a break to prepare.

1 - Gold Mimic(!!!) - A

2 - Thunder Crystal - A

3 - Emerald - B

4 - Fire Crystal - C

5 - Ring of Amaterasu - C
Accessory that increases LHT resist by 88%

6 - Flower - C

7 - Diamond - D

8 - Hiraishi - D
A set of medium armor with a massive Eva boost. Perfect for Aya if you haven't made much of her armor.

9 - Mirror-Plated Buckler - E (Left door)
A phenomenal magic shield with a decent activation rate.

10 - Water Crystal - E (Right door)

11 - Oni Lord Club - F
Decent "axe" with a decent Slayer effect.

12 - Gold Mimic(!!!) - F

13 - Veteran Kunai - H
Phenomenal knife with decent damage, a good Slayer effect, a high chance of Severe Poison, AND an increased crit rate. This knife really does it all.

14 - Earth Crystal - H

15 - Emerald Staff - I
Great staff for increasing Light damage, though it's only really useful for Byakuren or Satori as Reimu and Patchouli have better options with their personal weapons.

16 - Black Diamond - I

17 - Magic Dimension Robe - J
Huge MDef boost and a massive increase to max MP. Decent robe for Satori, but most other size S characters don't need that much of an MP boost.

18 - Platinum Mimic(!?) - K

19 - Rebirth Armor - L
Large armor with an inherent Endure effect. Incredibly helpful and worth considering over other armors.

20 - Strike Eagle Spear - L
Spear with a surprisingly high PAtk for having 50% Double Attack.

21 - Adamantite Shield - M
The highest PDef of any shield in the game. This shield is a must if you're tanking against phys-focused enemies with Alice.

22 - Chaos Shield - N
A physical medium shield with PDef on par with some large shields.

23 - Platinum Mimic(!?) - O

24 - Relic of the Gods - O

25 - Great Elemental Crystal - O

26 - Mythril Nugget - O

27 - Antinomy Blade - P
A decent sword with a good elemental resistance boost.

28 - Ring of Tsukuyomi - P
Accessory that increases DRK resist by 88%. If you've opened every other chest up to this point, you should get the Treasure Hunter achievement (because recipe chests don't seem to count).

29 - Recipes - Q
Chaos Blade, Caspar, Y Draig Goch, Incomparable, and God Idol-tier armor.
An upgrade to the blade Hina drops and all the best armors in the game, though you can't make any of the character armor until finishing the dungeon.

30 - King Mimic(!?!?) - Q
IGNORE THIS CHEST UNTIL YOU'VE ACTIVATED THE SHORTCUT TELEPORTER! It gets a guaranteed ambush and attacks four times per turn. Run Poison Shield formation with Alice and pray that all four hits target her. On turn one, use all your strongest attacks and try to kill it ASAP. If you're not confident in your damage output, use Quick Time with Sakuya to buy an extra turn.

Daremi Yoamarz Mondelica
A fast physical attacker with access to many of the skills from the Sword skill tree, alongside Angel Voice to provide it and its allies with an All Up. Fun fact! This enemy was designed by one of four winners of one of two official Touhou Card Monsters tournaments. 10% chance to drop the Dagger of Divine Speed.
Pretty low attack, but the Spd boost and Para chance are a nice bonus.
Found In - A, B, C, D, E, F, I, L, M

Blood Unicorn
The 999 MDef means most magic is effectively useless against it, so bring your physical attackers. Watch out for One Million Volts and its %HP damage, and make sure to pay attention when it uses Starlight Barrier.
Found In - A, B, C, D, E, F, H, I, J, L, M

Metal Shiisaa
An INCREDIBLY annoying support enemy. Having access to Reflect Wall, Starlight Barrier, AND Imposing Stance makes for a drawn out battle against its powerful allies if you don't focus it down immediately.
Found In - A, B, C, D, E, F, H, I, J, L, M, N, O

Neo Carbuncle
An enemy to loves to spam either Reflect Wall or Fatal PSN Claws. Stick to physical attacks only until it's dead.
Found In - A, B, C, D, E, F, I, L, M, N

Mass-Produced Terminator
I nearly screamed when I first saw this thing spawn in a group of itself. It's got all the capabilities of a normal Terminator with access to All target default attack with Slayer effects against the whole party and Murder Beam. Debuff its PAtk and Acc or rush it down with Thunder attacks (Gibnut Zarnica especially) IMMEDIATELY, and if you see more than one, hope to god you get a chance to flee.
Found In - A, B, C, D, E, F, H, J, L, M, N, O

Gold Mining City
The pinnacle of the Mining Villages we've seen so far. Absurd PDef and access to Imposing Stance and Starlight Barrier makes this thing an absolute pain to deal with.
Found In - A, B, C, D, E, F, H, I, K, N

Makai Gashadokuro
An incredibly bulky step-up from previous Gashadokuros we've seen. Rush it down quickly with Strike (preferable), Fire, and/or Light damage before it can deal too much damage to the party.
Found In - A, B, C, D, E, F, L, M, O

Firefox
An enemy that's only really notable for its decently powerful Fire attacks and its ability to set Fire land.
Found In - C, D, E, F, H, I, K

Mechanidragon MK-III
Kill this thing quickly before it can use Revolution Breath. Alternatively, if Aya is present, have her use Favorable Wind every turn to reflect it if it does happen. Other than that, just be ready to set a new field if it uses Mechanical Camo Barrier.
Found In - C, D, E, F, H, I, L, M, N, O

Azazel
An annoyingly bulky enemy with powerful Thunder attacks and the ability to set Thunder land. Hilariously, it regens exactly 2 HP a turn at max Thunder land.
Found In - C, D, E, F, H, I, J

Ryuuguu no Ouja
The most powerful of the oarfish. Kill it quickly before it can use Aurora Breath or have Aya on hand to spam Favorable Wind.
Found In - E, F, H, I, J, K

Hamadryad
A thankfully rather weak enemy with a love of spamming Exhaust. Have dispels or buffs on hand if you can't kill it quickly.
Found In - E, F, H, I, J, N, O

Type 10
An incredibly physically bulky and powerful enemy. Use magic, or don't bother.
Found In - E, F, H, I, K, L, M, O

Golden Tsuzuragaeru
A bulkier Tsuzuragaeru. It can show up rarely accompanying an otherwise normal encounter and will often flee within a turn or two. It's not particularly worth hunting down except for the Compendium entry as you have much easier ways of getting random item drops.
Found In - A, B, C, D, E, F, H, I, J, K, L, M, N

Note: Everything from this point on is found in the Great Library section onwards and is a step up in difficulty. Prepare yourself accordingly.

Fire/Water/Earth/Lightning Elemental
Powerful elementals that can set the land to their respective element and overwhelm with their elements. They're often accompanied by other enemies of their element.
Found In - (Fire) H, K, N, O, R ; (Water) H, K, L, M, N, O, R ; (Earth) H, K, N, O ; (Lightning) H, J, K, N, O, P

Vampire Girl
Not too notable outside their ability to drain HP and set Dark land.
Found In - H, I, J, K, L, M

High Master
The strongest of the ninjas. Powerful physical attacks, plus high Spd and Eva, plus a tendency to inflict instant death make these enemies incredibly dangerous.
Found In - H, I, J, K, L, M, O

Virgin Moh Shuvuu
A stronger version of the Moh Shuvuu found in Hieda Manor Basement. Just watch out for its All target Charm attacks.
Found In - J, L, M, N, O

Grudgekeeper
Another Horus bird, the bane of my existence. Be ready for Horus Barrier to shut down all your magic users.
Found In - J, L, M, O

Poison Giant/Thor/Utgarda-Loki/Surtr
A set of four nearly identical bulky, powerful giants, each representing one of the core magic elements. They all have access to Sake, a buff that increases physical damage dealt and decreases physical damage taken. Additionally, the Poison Giant can inflict Lethal Poison. Each one has a 4% chance of dropping the Nirvana Lotus Axe.
Incredibly high PAtk, plus 75 Exo, plus 50% defense ignoring, plus the fact that it ignores shields make this almost certainly the best axe in the game. Worth grinding for, even in comparison to personal weapons.
Found In - (Poison) I, K ; (Thor) I, J, K, N, P ; (Loki) I, K, N, R ; (Surtr) I, K, N, R

Empress Flayer
I saw this thing and screamed. They're really no different from other Flayers, but that's exactly what makes them An Absolute Nightmare. They're not worth dealing with, just run.
Found In - J, L, M, O

Chaos Dragon
The strongest of the Lesser Dragons, though they're not as threatening as they look. Whip out Marisa's Sparks, and you'll find its health dropping pretty quickly.
Found In - J, K

Artemis
The strongest Moon Resident. Kill it quickly before it can use Time Stop, especially since they often spawn as backup for other powerful enemies.
Found In - L, M, O

Lich Lord
Yet another Lich enemy. No weaknesses and high HP make it tough to kill, and it excels in various elements. Do your best to focus it down.
Found In - K, L, M, O

As one last note, the elemental Towers from the previous few dungeons are all back. Be ready for Imposing Stance as usual. They can be found in the following rooms:
(Hell) C, D, H ; (Babel) C, D, H ; (Ice) H ; (Gaia) I

This is largely the reason why this guide took so long. Just like the Gorgon Sanctuary and Depths of Resentment, the second half of the Barrier Distortion (specifically from the Great Library onwards) has room specific encounters with incredibly powerful enemies that you need to specifically prepare for. However, unlike with those dungeons, some of these enemies can be found in more than one room, and they don't always spawn alone either. As a universal strat, Sakuya's Quick Time is worth replacing almost any party member for its nearly two full free turns of safe attacks. Keep this in mind if you're ever struggling.

Glory Empress
Found in room H, the Glory Empress is one of the strongest random encounter demons. It has powerful elemental magic and can attack up to four times per turn. Prep your Light attackers with multi element resist gear such as the Kagami, Soli Deo, Garter Belts, Dragon Scales, etc. Reimu's Great Duplex Barrier, Satori's Reflect Wall, and Alice's Little Legion can all help nullify damage for a turn. 15% chance to drop the Astral Javelin.
Pretty good spear with high PAtk, a lot of Exorcism, a whopping 88% Mystic resist, and 35% extra Mystic damage on hit. A great choice for anyone running spears.

Resentful Shofet
Found primarily in room I and sometimes in room P, the Resentful Shofet is an enhanced version of the Shofet from the Depths of Resentment. It still has access to a plethora of column Slash attacks, but it now has Full Moon Revenge in its arsenal as well. Protect yourself well against Slash damage, and you should be fine. Interestingly, it's also vulnerable to instant death. 10% chance to drop the Gaia Armor.
Large armor with rather high PDef further enhanced by a 50% resist in all three physical elements. Great for Yuugi, who already gets a plethora of physical defensive effects.

Terminator Custom
Found primarily in rooms L and M and sometimes in room R, the Terminator Custom is an enhanced version of the Terminator from the Depths of Resentment. It still has Murder Beam and its All target Slayer default attack, but it can act three times per turn. Debuff its PAtk and Acc IMMEDIATELY, then hit it with Byakuren's Perfect Resist to keep it from dispelling its debuffs with Vortex. Interestingly, it's incredibly vulnerable to instant death, so spam Gibnut Zarnica with Satori to quickly kill it unless you want to give the kill to Akyuu. This can be a much preferable source of Weekends of the End to trying to get the materials to synthesize it instead.

Cernunnos
Found primarily in room N and sometimes in room O (alongside a High Master and Mechanidragon MK-III) and room P (alongside itself!?!?!?), the Cernunnos is a stronger version of the Crom Cruach found in the Gorgon Sanctuary. It behaves largely the same, spamming debuffs (including Tamatebako, an All target All Down), instant death, and using Pain Bond (deals Dark damage equal to the user's missing HP). Spam Light attacks to kill it as quickly as possible. Have Sanae and Satori on hand to revive downed party members, and if necessary, bring Sakuya to use Quick Time to reduce the number of turns it gets.

Paradox
Found primarily in room N (almost always alongside a Hamadryad and a Neo Carbuncle) and sometimes in room O (alongside a Virgin Moh Shuvuu and Empress Flayer), the Paradox is a more powerful version of the Ambivalenz found in the Gorgon Sanctuary. It behaves largely the same, spamming Void magic, though it now has access to Comet. With its immunity to physical attacks and Light and Dark, your options for damage are limited. Have Patchouli set an element at the start, and then spam exclusively that element with Patchouli, Satori, and Marisa (or use Marisa's Sparks instead). 15% chance to drop the Chaos Zero.
Large armor with very high PDef and a 10% phys reflect chance. Great armor, though not necessarily worth using over other options available.

Mac Lir
Found primarily in room O (alongside an Artemis) and sometimes in rooms L, M, N, (alone) and P (alongside Mordred), Mac Lir is a stronger version of the Druid found in the Gorgon Sanctuary. It has access to every single magic element, though it's by far the weakest of these. A single Quick Time is a death sentence, no matter the party setup, and even without it, a bit of element resist makes it just about unable to kill you. 10% chance to drop the Divinus Calix.
A staff with decent stats and a full 100 Exo. Not too notable beyond that, though.

Mordred
Found primarily in room O (alongside a Makai Gashadokuro) and sometimes in rooms L, M, N, (alone), and P (alongside Mac Lir), Mordred is a stronger version of Pendragon found in the Gorgon Sanctuary. It has high PAtk and PDef, along with access to powerful Slash attacks and decent regen. Bring a physically defensive party with good Slash resist, and it should go down without too much trouble.

Allocer
Found primarily in room P, Allocer is a powerful Earth aligned demon with up to three actions per turn and access to Earthquake, Mud Spray (a spread target Earth attack that can inflict Blind), PSN Hazard, PSN Breath, DTH Breath, PET Breath, and Leaf Barrier. Keep your Res high to avoid Poison (especially if PSN Hazard gets used) and Petrification, and keep up the pressure with Thunder attacks to keep Earth land low.

Elite Two-Headed Dragon
Found primarily in room P and sometimes in room J, the Elite Two-Headed Dragon is a stronger version of the Two-Headed Dragon found in the Gorgon Sanctuary. With up to two attacks per turn and an excessively high 3000 PAtk, nothing even comes close to this thing's damage output. Even fully kitted out with physical defense, Alice will still struggle to survive very long. Run Poison Shield, have Alice use Hourai Doll immediately, and then spam Marionette/Rainbow Parar on the back row. Have Sanae buff everyone's HP and PDef ASAP, and make sure to apply Wind of Miracles as well. Fully heal the party and revive downed members when necessary, and apply either a PAtk or MAtk buff whenever you can fit it in depending on whether you're using physical attackers or magic attackers (with Light and Mystic damage specifically). Sakuya's Quick Time is a godsend here. 15% chance to drop the Dragon Lord Slayer.
An incredibly powerful sword with a whopping 150% Dragon Slayer and even breath immunity. Grinding this out before tackling the Dragonlord is highly recommended.

Malicehedron
Found primarily in room P and rarely in rooms E and F (the only one I've ever seen spawn before the Great Library, and only once; it may spawn with a Yukkuri King in these rooms), the Malicehedron is a stronger version of the Marisahedron found in the Gorgon Sanctuary. It behaves largely the same, spamming Hit and Run along with Hedronite Beam. It's immune to magic, so physical attacks are your only option here. It'll take a while, but it's otherwise not too dangerous if you have a healer.

Nehasim Seraphim
Found primarily in room R and rarely in room K, the Nehasim Seraphim is a more powerful version of the Seraphim found in the Depths of Resentment. With up to three actions a turn, the ability to set Light land, and a plethora of powerful Light attacks, this thing can be a major threat. On any turn that Light land is at Max, it'll always use Punish the Judgment as its first action, a 700 power All target Light attack. Keeping a constant stream of Dark attacks from Patchouli, Byakuren, and Satori is the only way to have a chance of keeping up with the land war. If you need to set Dark Brand on a physical attacker (like Sakuya), use Quick Time to ensure you have time to do so without getting overwhelmed by Light land. Additionally, it WILL use Elixir at any point without any warning. Trying to fight it without Sakuya's Colosseo World active is a fool's errand. 15% chance of dropping the Archangel's Leotard.
Pretty decent small armor that provides a full 88% Light and Dark resist. Great for a few of the tough fights here, but it's otherwise not all that needed at this point in the game.

Bune/Haborym/Forneus
Found primarily in room R, Bune, Haborym, and Forneus are a trio of powerful demons that are largely identical outside their specialized element: Thunder, Fire, and Water respectively. Each one has up to three actions per turn and access to Damage Net (and will almost certainly use it within the first couple turns) and the tier three Marisa and Patchouli skills of their respective elements. Beyond that, Bune has Inazuma Slash and Accelerate (a Eva buff that also makes every action happen twice), Haborym has Moulin Rouge and Sake (a buff that increases physical damage dealt and decreases physical damage taken), and Forneus has OCTOPUS MAELSTROM and Growth (an All Up buff). Fully spec your party for the opposite element, set land immediately, and keep up the pressure. If they use their buffs, dispel them quickly. Forneus specifically has a 15% chance to drop the Archon.
Excellent defenses for small armor alongside a 5% boost to all magic damage. A decent choice that can be worth grinding for.

Chiyou
Found primarily in room R and rarely in room N, Chiyou is an incredibly powerful deity that resists Light, Dark, and all physical elements. With up to FIVE actions per turn, 1800 PAtk, incredibly powerful Slash attacks (including Impale Charge, which has Pierce targeting), incredibly high (if not total immunity) to debuffs, and 1999 regen per turn, Chiyou is by far one of the toughest (the absolute toughest, in my personal opinion) enemies in the entire game. I've only found one strat for killing it even semi-consistently. Bring Alice, Sakuya, Sanae, Marisa, and Patchouli in the Poison Shield formation. Alice should be in the decoy position in the front, and Sanae and Sakuya should be behind her. Sanae should be built for physical defense and Slash resistance, and Sakuya should have a Hairpin of Swiftness if you're not confident in her outspeeding Chiyou to use Quick Time. Alice should use Hourai Doll on turn 1, then spam Marionette/Rainbow Parar with the Adamantite Shield every turn after. Sakuya should use Quick Time on turn 1, Elegant Killing Doll on turn 2, and then Full Moon Revenge every turn until Quick Time is off cooldown. Sanae should use Wind of Shields on turn 1, Star Ritual to Call the Godly Winds on turn 2, Wild Excellent Luck Dance on turn 3, Wind of Miracles on turn 4, Wind of Prayers on turn 5, and Wind of Blades on turn 6. She should then reapply buffs and heal when necessary, interrupting the early turn order if health gets low. Patchouli should set any element on turn 1 (whichever you've built her to deal more damage with) and then spam that element's spell (and later skill after running out of bombs) every turn. Marisa should use Ultimate Spark on turn 1, Triple Spark on turn 2, and then use Rapidfire Master Spark/Super Magic Napalm/Final Laser (whichever is strongest and off cooldown) every turn until the spells are off cooldown. Even then, it'll be a long and rough fight, and you're still not guaranteed to win, especially when Chiyou still gets five actions. The fight can quickly go south at any moment. 15% chance to drop the Nitocris.
A decent spear, but it's nowhere near worth grinding for if you're not going for 100%.

Three-Star General
Found primarily in room R and rarely in room P, the Three-Star General is a stronger version of the Royal Duke found in the Depths of Resentment. It has up to three actions per turn, can set Dark land, and has access to many powerful Dark attacks (including Kagami's Dark Petit Flare Burst), Flare, and Vacuum Wave. If Light land ever hits maxes out, it'll start the turn with Chaos Land to heal 10k HP and drop the land back to neutral. Once it drops to 50% HP or below, it'll add Dark Giga Flare to its arsenal, often using it as its first action. Bring Alice, Byakuren, Patchouli, Satori, and either Reimu or Sakuya. If using Sakuya, Byakuren should set Star Sword immediately on Sakuya. If using Reimu, once it drops below 50%, alternate between Little Legion, Reflect Wall, and Great Duplex Barrier to protect against Dark Giga Flare. If running Sakuya instead, use Quick Time the moment its HP drops below 50%, and then use Reflect Wall and then Little Legion while you finish it off. 15% chance to drop the General Daemon's Arm.
By far one of the best shields in the game. 999 MDef while blocking all magic elements with a 90% rate makes you nearly immune to magic (outside Void) entirely, and that's before even mentioning the 10% damage boost to all magic elements. Absolutely worth taking the effort to grind for.

Dragonlord
Found primarily in room R and rarely in room O, the Dragonlord is a stronger version of the Dragon from the Depths of Resentment. It gets up to three actions per turn and has access to many powerful breath attacks and a plethora of Mystic spells, including a unique one called Nuclear Splash (All target Mystic spell with incredibly high power and cast speed). If it Concentrates, it'll follow it up with either Dragon Breath or Comet. While it seems threatening, it's not actually all that dangerous so long as you have Aya use Favorable Wind every turn and outfit the party with enough Mystic resistance. As for killing it, just pass swords to your physical attackers and spam Dragon Fang Strike. The Dragon Lord Slayer is the best choice by far and can even hit for 50k with Dragon Fang Strike if landing a crit while buffed in the Moriya Destruction formation. The Murakumo, Chaos Blade, and Kusanagi (in that order) are your next best options. If it does manage to Concentrate before it dies, have Alice on hand to Little Legion. Keep in mind that, just like the Dragon and Elder Dragon, it can use Elixir once it falls below 25% HP, though the DPS from this strat may never give it a chance to use it, and if it does, it won't be much extra effort to bring its health back down again. 15% chance to drop the Dragon Leather.
Great medium size armor with phenomenal resistances. Definitely worth grinding for, especially with how easy the Dragonlord is to kill.

If you still need to get the Anti-Releaser from the Elemental Emperors or kill them with Akyuu (or, god forbid, still learn Jesus Crush and/or Zalam Iblis), they can be found at the end of the Barrier Distortion alongside other enemies. They no longer get their guaranteed ambush turns, but their elemental themed backup means it'll be incredibly easy for them to fill the land gauge, at which point they'll begin using their spells every turn. For the most part, just prep spells of the opposite element, and bring down the backup first.

Fire Monarch - Room R
Accompanied by Surtr and a Fire Elemental.

Ice Emperor - Room R
Accompanied by Utgarda-Loki and a Water Elemental.

Thunder Czar - Room P
Accompanied by Thor and a Lightning Elemental.

Divine Sultant - Room P
Accompanied by a Will Galgalim and a Sophia Cherubim. Kill the Will Galgalim before it can Mental Blast too much.

Evil Shah - Room P
Accompanied by Tsukuyomi and a Midnight. Be mindful of Tsukuyomi's Reflect Wall until you kill them.

As soon as you're ready, step towards the shrine and confront the game's final challenge.
Chaos may look intimidating, but it's a bit more manageable than Chronos, at least. It gets three actions per turn and has access to a plethora of skills spanning all magic elements but Light. Expect to see Vacuum Wave, Fire Breath, Onibi, Cold Breath, Thunder Breath, Smoke Bomb, Acid Breath, Toxic Mist, Nerve Destruction, Flare, Peta Flare, Cosmic Liner, Dark Giga Flare, Void Slice, and Meteor. Additionally, it has access to two skills unique to it: Tartarus Hand, a single target physical Void skill that dispels, and Void Effect, an incredibly powerful All target magic Void skill that dispels. If it uses Concentrate, it'll follow it up with either Combinatio Nova, an All target magic Void spell with 100 Exo, or (if HP is below 50%) Supra Naturalis, an All target magic Void spell with 100 Exo that ignores barriers. On top of everything, Chaos is immune to Void, and its Unknown species means no Slayer effects will work on it.

Right away, it's important that none of Chaos' single target attacks (Vacuum Wave especially) hit anyone other than your tank. Run Poison Shield with Alice in the decoy slot, and use Hourai Doll on turn 1. From that point, she should use Marionette/Rainbow Parar every turn. Make sure she has both the Kagami and Magatama equipped. While the descriptions don't state it, they also reduce Void damage. This is unfortunately not true for the Regalia or Soli Deo. For buffing, stick with Byakuren and only buff Res on your physical attackers and PAtk/MAtk. Having more buffs active seems to make Void Effect more likely to be used. In order to deal with Combinatio Nova, use Reimu's Great Duplex Barrier or Satori's Reflect Wall to completely negate the damage. If they're both on cooldown, have Alice use Little Legion, and be ready to revive her afterwards. As for Supra Naturalis, the fact that it pierces barriers means that your only real option is Alice's Little Legion, so once again, be ready to peel her off the floor. Damage wise, stick with Light damage. That way, you can benefit from land power without Chaos getting the same benefits. Reimu should use Spirit Strike Particle Scatter to cap out Light land on turn 1, then use True Innate Dream, Dream Seal -Zero-, and Hyper Amulet for damage. Try to keep some bombs for Great Duplex Barrier. Satori should spam Punish the Judgment, then swap to Divine Gate when her bombs get low. Try to keep some bombs for Reflect Wall. Your last party member can be anyone, though I recommend either Patchouli or Youmu. Patchouli has a chance to double cast magic if the land power is high enough, and she can score crits with magic. If using her, spam Royal Flare until she runs out of bombs, and then use her skills in accordance to whatever currently has the highest land power. Youmu has a chance to use physical attacks twice in a row, and her DPS is incredible, especially if running Human Realm Sword Stance and Fearless Before Danger to increase her crit damage. If using her, set Human Realm Sword Stance and Fearless Before Danger on the first two turns, then use Matsuyoi-Reflecting Satellite Slash and Cycle of Reincarnation Slash whenever they're off cooldown. If spells are on cooldown or Youmu runs out of bombs, switch to Full Moon Slash and Crescent Moon Slash. Reapply her stance and crit buff whenever necessary. As for your commander, Mokou is your best bet. The passive endure chance alongside Phoenix's Tail and Phoenix Rebirth make her incredibly helpful for survival, and with enough bombs, she can even help you recover after a Void Effect or Meteor gone wrong. In terms of equipment, high level Moon Curtains and Galaxy Curtains are incredibly important, followed by multi-element resist accessories such as the Soli Deo and Hakurei Garter Belt, followed by PAtk/MAtk boosting and Light damage boosting equipment.

No matter what, it'll be a long fight, but with patience and perseverance, you should be able to push through.

Upon defeating Chaos, you'll receive another batch of recipes.
Specifically the Great Orichalcos Crystal-tier weapons.

Additionally, you can retake this quest at any time to revisit the Barrier Distortion and farm Chaos for God Idols. Returning to the shrine will also reveal the actual final two quests.
These two quests will give you Great Orichalcos Crystals and God Idols respectively for rematching the Three Goddesses and Resentment Incident with no actual changes to the fights themselves. If you've cleared every other quest up to this point, then clearing these last two should get you the achievement "The One Who Clears All".

Congratulations on clearing Genius of Sappheiros' final challenge. Give yourself a pat on the back, and enjoy the power trip with your new super hyper ultimate weapons as you wrap up the last little bits of 100% completion.