Comeuppance

Where most damage prevention asks you to eat the alpha strike and survive, this turns the wall into a mirror. It belongs to the small family of fogs that retaliate, in the lineage of older redirection spells like Eye for an Eye and Deflecting Palm, but it consolidates the idea into a single clean instant that blankets an entire turn. The split clause is the cleverness: damage prevented from a creature source is dealt right back to that creature, often killing the very board that committed to the swing, while damage from a noncreature source (a fireball, a burn spell, a damage-dealing artifact) gets aimed at that source's controller instead. The result punishes both the aggressive creature deck and the player pointing a large X-spell at your face, with no maximum and no scaling cost. The prevention condition keeps it fair: it does nothing against an empty board or an opponent who simply holds back, and it cannot touch noncombat life loss, mill, or any source you control. It also only redirects damage it actually prevents, so an opponent attacking someone else walks away clean. Within that window, though, it is one of white's most asymmetrical multiplayer answers, a held card that converts a table's worth of aggression into a single one-sided sweeper while leaving your own life total and planeswalkers untouched.