Originally Posted by
Lyth
I think that flashback from 5.3 is going to get clarified in Pandaemonium, actually.
When we first fight against Eric in P1S, Elidibus uses creation magic to 'summon some illusory allies' to our side, and the spell itself is very different from our usual summoning routine. I expect that at some point, Azem is bound to show up in that same Warrior of Light armor set from the flashback and show off that signature spell for the first time. Elidibus learns spells after observing them, after all.
The bigger question is why G'raha also has knowledge about that signature spell.