Grimm is planning to grease the wheels on one of the series' greatest mysteries in the 100th episode.

'Grimm' Season 5 Spoilers: Will Nick & Adalind Move In Together? A Baby Changes Everything

The NBC series is about to hit a major milestone, and the writers will celebrate by untangling the ever-elusive seven key storyline.

"We're going to explain the damn keys," showrunner David Greenwalt said at San Diego Comic-Con, according to The Hollywood Reporter. "We still don't know what they do but by god we're going to explain it."

'Grimm' Season 5 Spoilers: When Will The Loch Ness Monster Appear?

Interestingly enough, season 5 will see the Royals take a back seat. Considering how invested they are in obtaining the map hiding with in the keys, however, it's probably safe to assume that the Royals will have a role to play in the 100th episode.

As viewers anxiously await the next clue in the key mystery, Grimm has invited fans to create and submit their own wessen as part of the "Grimme Your Best Shot" contest. The winner will get the honor of seeing their creation join the series' rogues' gallery of monsters.

"You're our Grimmspiration! Seriously, Grimmsters, you're an integral part of the show. Literally!" the series announced on Tumblr. "This is your chance to design a Wesen that will debut in Grimm's 100th episode. Submit your own custom creature with the hashtag #Grimme Your Best Shot and one lucky Grimmster will win! See rules for details. You have until October 2 to enter your creatures."

Catch up with Nick Burkhardt and Co. when Grimm returns to NBC on Oct. 30.

Tags: Grimm television nbc