Hroki, The Ice King
Ragnarok, The Hellfire Dragon
Tiamat, Lust Incarnate
Karthuum, Stone Lord
Utmo, Terror Of The Deep
Zacyrath, The Mind Eater
Word of warning for when the fighting happens, all are incredibly powerful and are rival only by the gods. Even two gods versus one Leviathan is no easy fight so I don't wan't anyone smacking around any of these guys with ease.