Joined a game jam and ended up making a pretty interesting mechanic based on the sanity bars lots of cthulhu games have. This time isntead though, the boss has a sanity meter which you can wear down with abilities in order to make them vulnerable to damage and, although since this was a game jam I didn't have time, eventually in a later version change the way they fight (most of the time).
I plan on finishing a full version of the game to be done later this year but for now if you wanna check it out here's a link:
https://zayleradomi.itch.io/rive
And a link to the game jam which is all boss rush games: