Weapons:
(Demonic) Last Prism
(Ruthless) Raven Staff or Deadly Sphere Staff or Pirate Staff (Pygmy staff might work but I haven't tested)

Armor:
Nebula set
Stardust set (or Spooky set could work too)

Accessories:
(Lucky) Destroyer's Emblem
(Lucky) Celestial Emblem
(Lucky) Sorcerer's Emblem
(Lucky) Eye of the Golem
(Lucky) Celestial Shell (Celestial Stone also works fine)
(Lucky) Ankh Shield (any shield that prevents knockback is suitable)

List of potions in order of usefulness:
1. Magic power potion
2. Rage potion
3. Wrath potion
4. Pumpkin pie or anything that gives 'well fed' buff (buy pumpkin seeds from dryad)
5. Lifeforce potion
6. Heartreach potion
7. Endurance potion
8. Ironskin potion

Also use Super healing potions (you might get away with greater healing potions)

Material needed:

• Some building blocks
  
• Some platforms
  
• Some wire
  
• Wire cutters
  
• 1 wrench
  
• 1 switch
  
• 1 red/green/yellow pressure plate
  
• 1 bewitching table (can be bought from witchdoctor)
  
• 1 crystal ball (can be bought from wizard)
  
• 1 skeleton statue
  
• 2 crab statues (jellyfish, piranha and bat statues also work but drop lots of junk)

The three blocks to the right of the skeleton statue are actuated into the background then actuators removed.
Make sure you hammer the blocks to the right slopes (except the ones on the corners don't matter I just did it to look nice)

Wiring:


You can add a campfire and heart lantern if you want (I forgot to and it worked fine without)

A lot of people are having trouble with the skeleton not going through the wall because they didn't read the part where I said actuate the sloped blocks next to the skeleton statue even though I put it in bold. So here I will go into more detail on how to do it in an attempt to make my guide more idiot proof.

1. Make sure these three blocks are actuated into the background:


2. Now remove the actuators:


3. Then you can hammer the blocks into shape and do the wiring as previously shown in the guide


Of course add the statues too.
The three actuated sloped blocks let's the skeleton walk through the wall into the hoik.

1. Right click the bewitching table + crystal ball for the buffs
2. Equip your summoning gear
3. Summon 2 ravens in the crab statue box (a bucket of lava can be used instead if on normal mode)
4. Switch to nebula armor
5. Flip the switch
6. Make sure you have your last prism firing at full beam straight up ready for moon lord to spawn
and also use your quick-buff button to drink your buff pots
7. As soon as he spawns you should be hitting his head eye
8. When he closes his head eye, take out his hand eyes then wait for his head eye reopen
9. Finish taking out his head eye then kill his heart.
10. You can turn off the skeleton engine by killing the skeleton (solar eruption works well)

*Make sure you don't sweep the beam past the skeleton box or you could kill the skeleton (you can build 2 block thick walls to prevent this from happening)
*Drink a health pot during the fight if needed

*The crabs can drop mana stars when they die, with this set up it is enough to sustain the Last Prism mana usage
*Kill moon lord several times for more efficient use of buff potions
*You can potentially exchange the shield for a celestial stone for slightly more dps but it's more risky and you could die
*Sometimes you can do it without using a health potion
*If you die during his death animation you won't get any drops I uploaded a video of that you're interested

Please don't comment 'Using post moon lord gear blah blah blah" the whole point of the guide is how to speedkill not how to kill him for the first time.

I will try to answer any questions you have.