"From Alpha to Omega" may well refer to alphabetical order, at least for the summons, since most of them are elemental (elements combined). "Combined" may just mean when you put them together in a list.

Alexander
Chocomog
Ifrit
Leviathan
Shiva

And the towns could just be put either alphabetically, or in order that you visit them.

Ancient Forest Kalm
Kalm Mt. Nibel
Mt. Nibel Rocket Town
Proud Clod Proud Clod
Rocket Town Ancient Forest

I put Mt. Nibel second because you go there during the Kalm flashback.

I don't have any idea who it could be yet. Just putting forward some thoughts.