The four Raptor clans of the ancient Earth always held an uneasy alliance with one another. After a meteor devastated the Deathclaw Clan and unleashed strange creatures upon the planet, truces were made in order to find answers and return the world to order. The slime, a bizarre life form which oozed forth from the impact site, quickly spread to all corners of Laurasia, mutating native species and trashing the delicate ecology everywhere it appeared - threatening a mass extinction of all life on Earth.