Riot Control

The damage prevention is the whole defensive payload here, and the lifegain is a rider scaled to exactly the board it protects against: the more creatures swinging at you, the bigger the cushion before the swing even happens. That coupling is the design logic. A flat fog turns a lethal alpha strike into nothing, but it does no work against burn or a single large attacker; a flat lifegain spell pads your total but does nothing against an army. By tying the life payment to opponents' creature count, the spell self-corrects toward the situation it most wants to answer, the wide go-wide assault, while still functioning as a clean turn-long shield against any damage source at instant speed. It is a Fog with a buffer attached, and the buffer is largest precisely when the prevention matters most. The cost of that elegance is the same cost every fog effect pays: it buys a single turn and leaves the board exactly as it found it, so the life you bank has to convert into a real plan before the next attack step comes around. Riot Control is a one-shot pressure valve, built for the moment a multiplayer or token-heavy board threatens to end the game in one combat, and priced to be drawn into rather than planned around.