Zerstorer — formerly known as Skull Guy — is in Portland, and he's looking to make Diana (Hannah R. Loyd) his child bride so she can birth him a thousand children as he recreates hell on Earth.
We also know that he's got an interest in Kelly, but it's Nick who is in possession of what Zerstorer really wants: the stick. And he'll stop at nothing to get it. The ruler of the Other Place has already made it clear that he has no intention of showing anyone mercy, and his ruthlessness shows no signs of abating in the final hour of Grimm.
If Nick can't find a way to defeat the strongest enemy he's ever faced, then he'll be forced to choose between saving his friends and giving Zerstorer the one thing he needs to take over the world. His choice will have apocalyptic repercussions.