Well if the cult of the dragon has appeared in your game (it benefits both the Kuriotates and the Shealm, and both of them can take advantage of it). I'm not sure whether Acheron has roar, but bieng a dragon, it probably does.
Still, Acheron is the strongest of the three dragons in the game, so if you teamed him and Abashi in a stack, you would have a very powerful combo there. If Acheron has the mobility promotion in the first place that is.