Gargantua

Gargantua is a floor guardian on the fourth floor of the Great Tomb of Nazarick. It is a stone golem with height over 30 meters. Its arms and legs are chunky, so it may look cute if one does not regard its size. Red glow comes out from its chest like a heart.

Gargantua is not a custom NPC, but a bonus given from guild headquarters. Guild members named it as one of the floor guardians, yet it is just settled at the bottom of the lake in usual.

(Source: Overlord Wiki)