Dazzling Reflection

Two white staples fused into one slot: the lifegain scales with the threat, then the same swing gets blanked. A charging attacker pays you its own power in life, and the prevention then erases the next damage it deals this turn, so against one big creature this reads as a life swing and a one-target Fog stapled together. The cost of that double effect is in the targeting. The prevention is creature-specific and one-shot: it stops the next damage that one creature deals, not damage dealt to you, so a second attacker walks through untouched and a creature you target on offense gets blanked just as easily. Where it does hold the line is cleaner than the rate suggests, because combat damage is simultaneous: a trampling creature deals all its combat damage at once, so a single cast prevents the lot, both the spillover to the player and whatever lands on the blocker. The real tension is one of board state. The card wants a fat creature in play to be worth its mana, but a fat creature is exactly what you most need to defuse, so it points at an opponent's bomb rather than your own. White has always priced its lifegain and damage prevention at instant speed for this reason, letting the spell wait in hand until the attack step has fixed the numbers. The ceiling is conditional: a Fog that pays you, but only against one creature, and only once.