Welcome to the multiverse.

Hannah returns to Cthulhu in a week, and there's nothing Cain can do to stop it. Though he still has Soultaker, Hannah won't let him trade it for her freedom. The sword can summon an army of the dead, and Cthulhu wouldn't hesitate to use it.

It turns out Soultaker wasn't the only thing from the armory to survive. A mysterious cube was stolen by the mechanists. When Cain tries to retrieve it, he and Hannah end up in a parallel world where the mechanists reached the armory first and plundered it.

Using apocalypse weapons, the mechanists destroyed most of the coastal cities with tsunamis and have ground others to dust. To avoid destroying the world altogether, they're fighting a conventional war with airships and a small army of demigods. And if that's not formidable enough, they're also allied with Cthulhu.

Cain discovers the only way back to his dimension is by finding a device called the Tetron. To do that, he'll have to infiltrate the mechanists and steal it from them. But then, he discovers a nasty twist - the mechanists of this dimension plan to use the Tetron to invade other parallel dimensions. Cain's dimension is considered the original-Prime. And the mechanists have their sights set on it.

If Cain can't save this dimension, then his will also be doomed, and Cthulhu will ascend to true godhood.