Cocytus

Cocytus is the Floor Guardian of the 5th floor of the Great Tomb of Nazarick — a towering insectoid, part mantis and part ant, standing 2.5 meters tall. He was created by Warrior Takemikazuchi.

Cocytus has the heart of a true warrior: he respects an opponent's fighting spirit and takes pleasure in the battle itself, not just the victory. Unlike his more isolationist, xenophobic fellow Guardians, he's willing to welcome outsiders into Nazarick if they prove themselves honorably in combat, as the lizardmen did.

His own defeat at the lizardmen's hands taught him a hard lesson: after losing his army, Cocytus began reflecting more on his choices instead of blindly following orders, and eventually took charge of administering the very lizardman village he had once conquered.