O
Obedient
Obliviax
Octopus, Giant
Octopus, Octo-Jelly
Odem
Ogre
Ogre, Half-
Ogre, High
Ogre, Ice Spire
Ogre (Krynn)
Ogre, Mischta
Ogre, Nzunta
Ogre, Stonecrown
Ogre (Zakhara)
Omm-wa
Omshirim
Oni
Ooze/Slime/Jelly I
Ooze/Slime/Jelly II
Ooze/Slime/Jelly, Ghaunadan
Ooze/Slime/Jelly, Slithering Tracker
Ooze Sprite
Ophidian
Opinicus
Orc
Orc, Neo-Orog
Orc, Ondonti
Oread
Ormyrr
Orpsu
Otyugh
Owl
Owlbear I
Owlbear II
Owl, Space