Each enemy placement in Heretic has been replaced with a randomspawner.
There is forty-four or so added monsters in total.
I am a big fan of ShadowCaster and the Raven Software style sprites are so visually similar to Heretic that I think they fit.
I tried to find other mods that used the sprites and there were only a few here and there and not the entire bestiary.
There is also optional files for HeXen, Witchaven and Dungeons & Dragons: Slayer/Deathkeep monsters, as well as additional files to work with Wrath of Cronos RPG and Brutal Heretic RPG.
Spoiler: Downloads and instructions
Spoiler: Credits
Spoiler: Screenshots
Spoiler: Changelog