Fog

One-turn defensive spells that prevent all combat damage that would be dealt, stopping an alpha strike cold no matter how many attackers come in. Fog is the namesake; Moment's Peace returns via flashback for two fogs, Constant Mists carries buyback for a repeatable wall, and Arachnogenesis adds a token swarm on top of the prevention. Distinct from Protection Spell, which saves one creature with hexproof or indestructible instead of blanking the whole combat, and from Regeneration, which replaces a single creature's destruction rather than preventing damage across the board.