MoC was one of my favorite mods when I first started modding, but as people familiar with it know, it was murder on performance. It also relied on the mob spawner mod which broke mob spawning of every other mod. MoC Extended fixes all that. Well, mostly. It now uses the vanilla spawning system and the lag is mostly gone now, but I still notice a moderate tps hit in mob dense areas, so limiting ambient mob spawns with another mod might be a good idea. MoC Extended also revamped many of the models and textures, so the aesthetics are much closer to more modern mob mods. Still one of the best mob mods available for 1.12. Did I mention there are fairy pegasi? There are fairy pegasi.