I heard somewhere that red vengeance had some effect that one might not deduce for power challenges.
My interpretation is that, in a joust, if the defending player plays red Vengeance in response to the claim effect of a power challenge, the attacking player must simply steal the power from himself. In a melee setting, the defending player can choose an uninvolved player as the new target, taking that power from the uninvolved player to the attacking player.
Am I close?