Win a game on a board with Air RaidAir Raid Every 5 Chapters, all units will take 1 damage at the beginning of the Chapter. in play (must be a main event, and not through MysteryMystery Every 5 chapters, causes any Field Event to occur.)
Ways to Complete
The only map that includes Air Raid by default is Warfare, but adding it as a field effect on to any map in single-player or multiplayer still counts. In light of this, the Regeneration field effect can be coupled along with it to instantly negate the damage done, really making this achievement a snap. At the same time, be wary of other players' attacks and damage-dealing cards and traps. It's advisable to use characters such as Fernet or Kyoko, as their high defense and hp improve their survivability dramatically compared to other characters.
Be sure to stock plenty of healing cards such as Pudding and Saki's Cookie in the event of too much damage, and defense-increasing cards such as Rbits against strong attackers and bosses.
If you have the Mixed Pack DLC, Tactical Retreat is a great card to bring to avoid problematic fights.