Diabolist

Diabolists spawn in dungeons after hardmode is activated and Plantera has been defeated. They rapidly teleport and fire blazing magic bolts at you that go through walls. The bolts then explode where they hit and create an "Inferno" - a large flaming ball that does massive damage. Diabolists, like other hardmode caster monsters in the dungeon, will teleport on each hit, making them more difficult to dispatch.

They are immune to the Poisoned and Venom debuffs but strangely vulnerable to Cursed Flames.

They spawn in dungeons with Tiled Walls.

Tips

 * Diabolists follow the same pattern as Necromancers, but their shots go through solid blocks, so cover is not an option.
 * 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.
 * Homing weapons can continue to track Diabolists after they teleport.
 * Minions are effective against Diabolists, as they will automatically find and track enemies outside of the player's line of sight. Many can pass through walls to reach Diabolists as well.