Is it possible, that the demon - a modified fury - can only attack every 3 rounds, because his only available attack option is this flyby thing which a recharge rating of 3? I couldn't find any other attack actions for him. Ok, he could do the chaos mumbling thing, but I had do let him fly over the pcs for 2 rounds before attacking again. He was good, but not especially awful, eventually he was shot from the sky. A bit anticlimactic, my group only had a sense of panic, because two of them got unconcscious through the terror effect after he appeared.