what is a void creature?

phaneub17_ESO

I was thinking Dro-M'athra, but I killed a bunch and they didn't count.

SeaGtGruff

According to the tooltip, they're the void creatures in Blackreach, below the Reach. I ran all oved and couldn't find any at first, then eventually I made my way to the Library of Arkthzand and was able to kill several of them as they spawned from the void energy spheres in the big courtyard of the library.

MechanicalMudcrab

Got mine from shades and void rots outside of the Library of Arkthzand as well

spartaxoxo

I got mine from doing the Void Mother boss in the reach, it was also my reach daily. So 2 birds with 1 stone was nice.