The Cursed Magma Skeleton.
The Cursed Magma Skeleton is one of the 9 Superhardmode NPCs. It spawns in below the lava line, and has a maximum HP of 1000. This NPC can inflict the Cursed Inferno debuff on the player, and does 100 base contact damage. It has 60 defense, and drops ~1 Gold Coin on death. There is also a very small chance for it to drop a Cursed Flame or a Fire Shard as well.
In the source mod, it has a chance to drop the Greek Extinguisher.