Dawn kindly jumped into the MVP Arenas to check what's in there, for SCIENCE. Here's what we found:
Alpha - eddga, mistress, moonlight flower, maya
Beta - phreeoni, orc hero, orc lord, giant whisper
Theta - drake, doppelganger, osiris, lord of the dead
Epsilon - incantation samurai, pharoah, dark lord, baphomet
Each of the eight rooms for each type seems to contain random assortments of the above MVPs.
Also, TSO - the MVP lobby has a free healer, you should do something about that.