Necromancer

The Necromancer is a hardmode dungeon NPC. It can spawn in the dungeon when Plantera has been killed.

It attacks by firing beams of purple light 6 times at the player which do significant damage. It can be extremely dangerous, as the beams reflect multiple times off walls and travel instantly, making it difficult to reasonably avoid its attacks. Their beams inflict the slow status.

Whenever it is attacked, it will teleport. This makes the Necromancer frustratingly hard to kill.

However, one easy way to kill them is to play their game with the Shadowbeam Staff that they drop. The easiest method by far is using the Piranha Gun or the Scourge of the Corruptor, both of which will follow them to wherever they teleport to so long as the trigger is held.

They are immune to the Poisoned and Venom debuffs and only spawn in dungeons with a Brick Wall.