Known as the Conqueror of Legions and Eater of Limbs, Krass-skull is a supposed hidden boss enemy within the game. In actuality however, it's really just a running gag-esque joke the developers add into the update notes periodically, similar to how Mojang speaks of Herobrine in their notes. Krass-skull is supposedly the most difficult boss in the game having abilities like a four hour invincibility phase and being able to fire semi-homing shots that deal 200% base damage on hard mode. According the the developers, there have been problems with Krass-skull in the past, such as when it began spawning on the early floors, terrorizing players. However, it seems that no matter how many times they patch the game, something always seems to go wrong with this character.