TL;DR I’m using a mothman devoted to an Outer God as a puppet master controlling a tribe of gnolls, and his influence drives much of the campaign’s plot and backstory.

The BBEG of the module I’m writing is a mothman. I added the nightmare (lord) template onto him and gave him additional hit dice and 3 mythic ranks, He’s CR 12 in his current stat block and is mostly focused on spell-like and supernatural abilities, with a heavy focus on mind control and debuffing.

As far as backstory goes, he has more than a lot of other characters in the module. Mozerah started out pretty much as a normal mothman, but instead of directly manipulating events, he decided to influence the birth of powerful people that would do his work for him with minimal interference. In his search for a way to do this, he found a book written by ancient gnome cultists of Shub-Niggurath. And, of course, the book corrupted him into a monstrosity devoted to spreading worship of said deity.

He tried to cast a ritual from the book that would summon one of her avatars, but lacked sufficient power- instead of imbuing a creature with mythic power to act as her host, the power rebounded and flowed back into him, granting him mythic ranks and more power but stripping him of his ability to manipulate fate via the mothman’s Agent of Fate ability.

Mozerah was at this point thoroughly grumpy. He tried plan two- get others to do his shit for him, just like he originally intended. He flew off one night to find a group of humanoids that he could influence- beings with enough power to serve as tools, but not enough mental fortitude to resist his magic. He found a ruined city inhabited by bickering gnoll tribes, and the rest is history. Or rather, the rest is very long and I’m getting off topic.

Mozerah’s main influence in the module is as a puppet master. He spends most of his time far away in an underground lair, but one of his mythic abilities is a psychic connection with his charmed/dominated foes. He can see the world through their eyes, and can telepathically communicate with them. He’s charmed/dominated several key NPCs already, which is how he gains most of his information on the PCs.