Nice effect, but shouldn't it have a drawback, like destroying the permanent targeted by Aegaeon's Retribution after x turns, damaging the creature targeted by Aegaeon's Retribution by x hp per turn or poisoning the player targeted by Aegaeon's Retribution by x poison counters? I mean, if you are covered in acid, you are going to damage whatever touches you, but you are being damaged from the acid too.
Furthermore, This won't really help as an anti-PC against SoFo; quite the opposite. Those 10 points of damage dealt to SoFo are going to allow it destroy +1 permanents before turning into a Black Hole. Maybe making a change here?