Cthulhu Mythos: Yig Snake Granddaddy - Act 4: The Ancient Ages [5E]

With their enemies on the defensive, the heroes must try to knock both the Yithians and the Elder Things out of the war. But can they successfully campaign against entities who are wiser and more intelligent than even the smartest human?

Even if they succeed, it is to discover that nothing is more dangerous than a cornered snake. The serpent wizard plots to sacrifice an entire city to Yig and summon the Great Old One himself in an apocalyptic rain of deadliest venom. Can the heroes defeat Yig in person?