The insect enemies are described in Endless Legend as "a Hive-people that survive by ingesting or converting others as they infect them with their plague, the Necrophages are scavengers and survivors. Always hungry and always hostile, they are viewed as a scourge by other peoples."
Necrophages are some of the earliest enemies you will encounter in the dungeon, the smallest ones often appearing behind the first door. At five different mobs, they are also the most numerous enemy species currently in the game.
The hero Skroig is also a necrophage.