Harmless Assault

The asymmetry is the whole design problem this card solves. A Fog stops everything in combat, both your attackers and theirs, which is fine when you are purely defensive but useless on a turn you want to race or alpha-strike back. This narrows the prevention to attacking creatures only, which lets it sit in front of a lethal swing while leaving your own blockers free to gang up without dying and, crucially, preserving any combat damage your defenders would deal. At four mana it pays a steep premium over the one-mana Fog baseline for that wrinkle: the cost is the price of one-sided combat. The window it exploits is the same one every Fog effect lives in, the declare-attackers-into-declare-blockers gap, where holding an instant that erases a board's worth of offense turns a board state that looks lost into a stall you survive. Where a generic Fog buys time symmetrically, this one buys time while letting you keep punching on defense, a distinction that matters most against decks that have overcommitted to attacking and left nothing back. It is a defensive trick built for players who want to weather a turn without surrendering their own clock, which is exactly the constraint that separates it from the cheaper, blunter prevention spells it descends from.