text: Whether the targeted player is still a legal target is no longer checked after Vengeful Archon’s ability resolves. For example, if a player targeted by Vengeful Archon’s ability puts Leyline of Sanctity (which says “You can’t be the target of spells or abilities your opponents control”) onto the battlefield after the ability resolves but before it prevents damage, the ability will still prevent damage and still deal damage to that player. If Vengeful Archon can’t deal damage to the targeted player (because the player is no longer in the game in a multiplayer game, for example), it will still prevent damage. It just won’t deal any damage itself.