Undead Rot Resist

At the same time, black bubbles appeared around him, and from them
emerged demons of around level 30 or so, Rotting Demons. They were over two
meters tall, with tarry black skin that resembled bubbling swamps. The bubbles
rose to the surface and burst, releasing a yellow mist. Despite being surrounded
by these demons who were wreathed in rot-inducing gas, Suzuki Satoru was not
affected, because he was undead.

There were 32 of them in all.

Suzuki Satoru shrugged.

- Overlord; Bonus Volume; Chapter 4