Oak
  Obliterator
Obscenery
  Obscure
Obsequies
Occult
Öde
  Ominous Dark
Omnihierophantom
Onheil
  Onraad
Onrust (Yawgmoth)
  OP
  Opacity (Opacity Of Evil)
Opacity Of Evil
  Ophiuchus (Cloak Of Altering)
  Order Of The Source Below (Dodecahedron)
Ordo Draconis
Orewoet
Ornaments Of Sin
Orodruin
  Ostracised