As far as I know
Duma auracite have Argath's aether - manipulate Ba'Gannam (Maybe wait for "Bloodline" to discover itself by Ultima's guide?)
Otius auracite have Ultima's aether(?) - manipulate Alma as Mikoto believe(?)
Tia's Virgo auracite have Orran/Alma's aether(?) - manipulate Jenomis to wander at Lesalia(?)
Ba'Gannam's Virgo auracite have Ramza's aether - manipulate Ramza(Bas) to guide WoL for final battle with Ultima

Please correct me if I'm wrong, I'm so confused now