I have an idea.
1.Shadow World
2.Necromancers,corrupted spirits,shadow men,shadow golems,wraiths,poltergeists,hell hounds,wither skeletons,wither,summoning temple,wither creepers,blood slimes,terror wood,wither brick,2-tailed vampire cat,corpses,coffins,crypts,burned sticks,corrupted gems,death scythe,grimm reaper.
4.Minecraft forge
5.Necromancers summon corrupted spirits,coffins let you sleep till night,grimm reaper is the second boss and it drops a death scythe,crypts have coffins and corpses,summoning temple is made of wither brick and has shadow men,shadow golems,wither skeletons, and the wither as a boss.