Future expansions.

look at the armor of Raialg from the 6th game and you'll understand that this is not a warrior
he doesn't look like a mage either, there's no staff.

This is actually a warrior, which is clear from his sword. However, with such blurry art, it's hard to tell much.

Raialg in the "fifth" game was a mage. It's quite possible that in that video he is one too, so determining the class of the creature based on Raialg's armor in this art is incorrect.