Diabolist

Type	Undead Enemy
Environment	Dungeon
AI Type	Caster AI
Banner	Diabolist Banner
Immune to
Debuff	On Fire!
Debuff tooltip	Slowly losing life
Chance	100% (projectile)
Duration	8–1516–30 seconds
Coins	153750
Hurt	https://terraria.wiki.gg/wiki/File:NPC_Hit_2.wav
Killed	https://terraria.wiki.gg/wiki/File:NPC_Killed_2.wav
Attack	https://terraria.wiki.gg/wiki/File:Item_20.wav
Fireball explosion	https://terraria.wiki.gg/wiki/File:Item_74.wav

The Diabolist is a Hardmode enemy found in the post-Plantera Dungeon. It is most common in areas backed by Tiled Walls. These are identified by the related Faction Flag, the Diabolic Sigil.

Diabolists attack by firing blazing magic bolts that can travel through blocks at the player. These bolts explode, creating a large flaming sphere that lasts for 3.83 seconds and deals massive damage on contact. Both the bolts and the spheres inflict the On Fire! debuff. Diabolists teleport to a different location on-screen every time they are hit.

Variants

Classic

Expert

Master

2 values: Pre-Hardmode › Hardmode
3 values: Pre-Hardmode › Hardmode › Post-Plantera

NPC ID	Type		Health	Damage	Defense	KB Resist
285		Red Diabolist	200/400/600	50/100/150 (melee) 80128192 (ranged)	12	30%/37%/44%
286		White Diabolist	250/500/750	60/120/180 (melee) 80128192 (ranged)	10	35%/42%/48%

Notes

Diabolists can only teleport onto solid blocks. If there is no valid place to teleport to, they will remain in the same location.
They are only able to teleport while resting on a solid block.

Tips

Since a Diabolist's shots go through solid blocks, taking cover is usually not an option.
Weapons that stick to enemies are exceptionally useful, as they remain on the Diabolist after the teleport. The Piranha Gun, Daybreak, and Bone Javelins are viable options.
Weapons that deal high damage in single hits are effective against Diabolists. Weapons that fire multiple projectiles simultaneously may be able to land multiple hits before they teleport as well.
Weapons with homing capacities or minions can continue to track Diabolists after they teleport.
Like other caster AI enemies, Diabolists cannot teleport to any space less than 4 tiles or more than 20 tiles from the player's feet, will not teleport to blocks covered in lava, require at least 2 solid blocks (or platforms) and a clear space of 2×3 tiles to teleport to, and will not attack if constantly damaged. These facts together can be used to set up a safe Dungeon farm if the only space they can spawn in/teleport to has a pressure plate with Spiky Ball Traps.

Trivia

The Bestiary entry for the Diabolist: "The undead who bear the Diabolic Sigil wield flames as intense as any in the underworld, consuming all in a scorching inferno."