From TMW: rEvolt
May mutate 2 attributes up to 30%.
The Larvern is found when doing the Rossy Quest, and is the slowest moving monster in the cave area. It is a scavenger, and will pick up the loot dropped by the other monsters.
It is highly recommended to save at least one of these creatures until last per wave of the cave attacks, as eliminating all of these will bring about the next wave of monsters, or end the event, leaving you to battle for air in the cave until the other monsters are gone.