Ai art made by me, I've always found the concept of a Grimm version of Cthulhu interesting.

Plot - Something more ancient and Demonic that even Salem fears, a ancient being that had became a Grimm, but does not follow any commands given by Salem. Instead, he does want he wants to.

After the Fall of Beacon, Remnant was never the same. After the Wyvern Dragon had be reawoken from its slumber, it wasn't the only thing that had been awoken from its slumber. Cthulhu had also been awoken from his slumber, the terror if the Grimm were just the start of something greater. Salem felt the shift in the air, the way the Grimm seemed to disobey her. The God's of Light and Darkness had sealed away this ancient being before, but the stories that were told of this giant beast were scrubbed out and forgotten.

Now with him being awoken yet again. A thick fog began to arise and swallow Remnant, through the fog his figure could be seen. A silhouette depicted as God like deity, boats vanish without a trace. People and Faunus vanish into thin air, the Grimm obeying something new, something ancient. No longer did Salem have control over the game of chess.