From Dungeons of Dredmor Wiki

Damage: (1 + *0.45)

Zalgohit1 is necromantic attack that can be triggered by other spells such as Fell Power and Eldritch Inhabitation. The damage from this can be used as a DOT against the character or a minor direct damage effect that procs on hitting a monster.

It is a side-effect of spells cast by characters with the Necronomiconomics skill tree, and part of the side effects of consuming a Potion of Dire Empowerment or from a Tentacular Infestation Bolt.