https://www.drivethrurpg.com/product/449052/Bumps-in-the-Night-Monster-Generator-for-Something-Strange-Genesys
The infinite multiverse gives rise to all manner of creatures, monsters, beasts, and mutants. Now GMs can randomly generate adversaries to frighten and challenge their players. Bumps in the Night takes inspiration from Secrets of the Crucible and the Expanded Player's Guide to give tools that not only give GMs the mechanical details necessary for a monster, but also appropriate narrative flair. It also goes beyond those simple details but offers ways that your monsters interact with the world through Mischief. Do they leave a trail of bodies behind them or just cause the local town to all experience Strange Visions? Additionally, Vulnerabilities are available for the PCs to discover to give them the edge (or the only way!) to stop the creature.
This resource provides a detailed but flexible system for generating unique monstrous nemeses. It goes beyond just generating their stats (though it certainly does that), and includes narrative and adventure context such as monster Origin as well as the Mischief it's getting up to and the Vulnerabilities that can be used to take it down for good.