Raubahn mentioned that Lolorito told him what Ilberd had planned while Raubahn was still in captivity, that after he had executed Raubahn he was going to arm the Ala Mhigan refugees with weapons paid for by the Monetarists and, presumably, lead them on what would be a suicide mission to take back Ala Mhigo. Instead now it seems he has some other 'power' as his secret weapon, which.... could be anything (I have my suspicions and theories... but I'll keep them close to my chest for now

).
Either way, apart from the exiled heir to the throne of Ala Mhigo's monarchy (whose name eludes me at the moment), there really isn't anyone else it could possibly be
other than Ilberd. He's single-mindedly determined to restore Ala Mhigo from Garlean control to the point of zealousness.