[Flyndaran]

Gaia Strikes Back: a collection of realities where the earth itself seems to develop strange defenses against the human threat.

Allergy: over a few years span, every human develops severe to lethal allergies to all wild plants and animals. Only hydroponically grown plants and animals fed on them all within sealed enclosures fail to induce the problem This means only a few vaults of survivors remain while the rest of the earth appears normal. Visitors may or may not develop such allergies.

Berserker: All wild animals go berserk whenever smelling humans inducing homicidal rage. Only domestic pets raised from birth are immune... usually. That scratching at the wall just got a whole lot scarier than "just mice".