This guide's main aim is to allow players to complete all of the achievements for Lost Eidolons.
I have not previously made any guides, but I enjoyed playing LE and as there are a few easily missed achievements and no similar guides that I could find, I thought I would give it a try.

I have tried to avoid spoilers for the most part and kept quest details fairly vague, but some of the achievements do tie-in to game events/endings and so a minor spoiler warning applies.

These achievements are story related and cannot be missed. Just complete the relevant chapter to unlock them.


The First Step - Complete Chapter 3: Breakout



First Blood - Complete Chapter 4: Break of Dawn



Monster Hunter - Complete Chapter 6: Murder of Crows



Monster Slayer - Complete Chapter 12: Into the Breach



Awakening - Complete Chapter 16: The Bloody Banquet



Huntmaster - Complete Chapter 17: Biding Time

Life or Death : Finish the game on Hard and Maniac mode.


Hard mode can be quite challenging, particularly if going in blind, as some chapters are much trickier than others and Maniac mode makes taking losses even worse.
You can still make use of the "Undo" function, although you have fewer attempts on Hard.

During a playthrough, you can adjust the difficulty down, but not up, so you can try starting out on Hard and then dropping the difficulty down if things get frustrating.
There is also an excellent "New Game Plus" feature which allows you to select what you want to carry over to the next playthrough, including gear, stats, levels, skills, money, items, or all of the above, which can make things much easier.

I would recommend doing a normal run to experiment with characters, builds, etc and unlock one of the endings (King/Warlord) and then doing a second run on Hard once you have a good idea of what works well and unlock the other endings/romance options during this run.



The Unvanquished : Win all battles without any allies withdrawing.


This refers to your units (blue health bars) and not friendly NPC units (green health bars).
When a unit is killed it "withdraws", so you need to complete all battles without losing a unit.

- Losing a unit in the first tutorial mission where Eden needs to escape does not void this achievement.
- Losing friendly "green health" units does not void this achievement.
- Restarting battles, or using the "Undo" function does not void this achievement.

There is a mission (CH 21) where moving next to green units turns them blue and brings them under your control. If you don't move a unit next to them, they remain green units and they can be killed without voiding the achievement.

When completing CH21 I left most of these units green and kept any blue health units alive.

Another player has reported that losing these extra units does not void this achievement:

Credit to GriffinPilgrim from comments section:
"For "The Unvanquished" I can confirm that you don't need to keep the extra troops from Ch21 alive, even after they turn blue and come under your control. I lost one but never lost any of my normal troops in any battle and still got the achievement."

In the later chapters of the game, there are certain points where you can make dialogue choices that affect the "Gaze of Venezeus" - which affects the scenes at the end of the game and are tied to some achievements.

There are four "Gaze" dialogue option points and choosing the generally paranoid/negative option strengthens the Gaze of Venezeus, (icon goes red) while choosing the generally trusting/positive option weakens the gaze (icon goes blue).

During the final battle, there are also two chances to increase the strength of the gaze to counter some of the final boss's power.
Using it reduces his regained health, applies a debuff, replenishes your spells and abilities and counts as a "red choice".
Not using it counts as a "blue choice", but the fight is more difficult.


"Gaze of Venezeus" dialogue choice example.


To unlock "Way of the Warlord", select a majority of red choices.



To unlock "Way of the King" select a majority of blue choices.


(NOTE: I have not tried every possible combination, but selecting all blue dialogue choices and then using the power twice (red x2) in the final battle still unlocks "Way of the King". For "Way of the Warlord I just selected all red choices and used the power twice).


The choices are:

-CH 20
- "Ouch" (red choice)
- "Joke about it" (blue choice)

-CH23
- "Can't be too careful" (red choice)
- Klara's not like that" (blue choice)

-CH24*
- "Can't trust anyone anymore" (red choice)
- "I'm sure there is an explanation" (blue choice)

*NOTE: The red choice here affects dialogue with Marchelle and locks out her romance option (see Part 5)

-CH25
- "I won't stop using this power" (red choice)
- "Thank you for telling me" (blue choice)

-CH27 (twice during boss battle)
- Call upon power (red choice)
- Ignore it (blue choice)

There are six "romanceable" characters in the game - Albrecht, Andrea, Johanna, Klara, Marchelle and Sera.

To choose one of them, raise your rapport level with them to 3 (via chats, giving gifts, etc) and then give them the unique gift item "Memento Box" - sold by merchant Salma in camp CH 26.

This locks them in as your selected partner and there will be a short dialogue scene with them just before the final mission, as well as a post-game scene.






NOTE: Sera and Andrea are mutually exclusive romance options - depending on which one of them you support in the choice in CH 19, one will be available as a romance choice but the other one will be "locked out", even if you max rapport and give them the Memento Box (you will often get a romance scene with a different character who you have high rapport with instead).

It is also possible to "lock out" Marchelle as a romance option by selecting the option "Can't trust anyone" during the CH 24 "Gaze Choice" (see Part 4).

It is useful to make a save at CH 19 camp, before making the choice between Andrea and Sera, then pick one, proceed through the game following either "Way of the King" or "Way of the Warlord" paths, unlock their achievement and then reload and make the other choice.
Marchelle's romance is easiest to unlock when following "Way of the King" choices.


The dialogue (and achievement) for each character pops up as soon as you leave camp to start the final battle (but the scene plays out before the final mission actually begins), so you can:

- Save up gifts throughout your playthrough (always buy all gifts from Salma's shop, save up unique/legendary gifts)

- Make a save in camp at CH 26

- Give gifts to max out rapport and then give the Memento Box to one character

- Launch the final mission to unlock the achievement, then re-load and repeat for a different character

With 100 leadership and rare/legendary gifts, rapport can be maxed out, even if you had low amounts from previous chapters.
It takes roughly 8 legendary + 8 rare gifts (using up 80 leadership) to boost rapport from zero to maximum for one person (many characters will gain rapport from chats/meals/etc so they will probably have at least a bit of rapport). Unique gifts give a large amount of rapport and can speed this process up.




A Promised Voyage - Learn Albrecht's true feelings.




Till We Meet Again - Learn Marchelle's true feelings
Can be missed if you select the "Can't trust anyone" Gaze dialogue choice in CH 24.
Recommended to unlock while completing "Way of the King".



Someone To Protect - Learn Andrea's true feelings
Only available if you agree to Andrea's request in CH19 and send Sera with Marchelle



Lean On Me - Learn Sera's true feelings
Only available if you deny Andrea's request in CH 19 and let Sera decide what to do.



First Bloom - Learn Johanna's true feelings




Let Us Cling Together - Learn Klara's true feelings

These are tied to optional side quests and can be missed if the quests are not completed. Some of them have rapport level requirements that must be met for the quests to be available. If the side quest is not yet showing, try completing other quests/chat bubbles.


Ready to Learn : Complete the side quest "Monstrous Studies"

- Available in CH 4



Earning Trust : Complete the side quest "A Commander's Gift"

- Available in CH 5




Broken Oath : Complete the side quest "My Brother's Keeper".

REQUIRES LEON RAPPORT LVL 2.

-Before CH 16, raise Leon's rapport to at least level 2. This unlocks a short side quest involving him. Complete this and then after CH 16, there is another side quest - complete this to gain a unique accessory and unlock the achievement.



Digging Deep : Complete the side quest "reaching Within".

- During CH 17, after you defeat the Vermiliths, you must defeat a Behemoth. Use Eden's special ability "Thunder of Venezeus" on the Behemoth (doesn't have to kill it, just needs to be used).
Once back in camp, a side quest will be available which will grant a unique sword and unlock the achievement.



Book of Malice : Complete the side quest "Malice and Greed".

- Available in CH 18. Check out merchant Salma's inventory (no purchase needed). After closing it, you can speak with her to begin a side quest involving a unique dark tome. After talking to a few characters, you can then either buy it from her for a discounted price, or complete an optional battle to gain an item she will trade it for.



House Vulisica's Heirloom : Complete the side quest "No Stone Unturned"

- During CH 20, speak to Karel and Fransico to unlock a side quest called "Rock of Aegis".
Complete that and later in CH 22 another side quest becomes available - fighting an optional battle grants you a unique shield and unlocks the achievement.



Arrow in the Wind: Complete the side quest "The Winds of Change".

REQUIRES ROBIN RAPPORT LVL 3.

- Before CH 23, raise Robin's rapport to level 3. This unlocks a short side quest involving him. After CH 23, another side quest will be available which grants you the weapon "Robin's Old Bow". Equip it on Eden and complete any battle (only needs to be equipped on Eden, it does not have to be used in an attack).
This unlocks another short quest that grants a unique bow.




BONUS OBJECTIVE:
Although there is no achievement related to it, there is a side quest related to Gilbert which can be easily missed.
You need to raise Gilbert's rapport to level 3 before CH 25. This will unlock a side quest during CH 26 - The quest begins from a speech bubble on Linard, rather than a side quest icon so it can be easily missed.