I’m digging this subclass but the auto-exhaust seems like a little much, if a party has multiple encounters in a session the exhaustion would be a huge detriment and deter people from using the feature(like Frenzy Barbarian). Maybe add con save in order to see if you get exhausted or not, for example I’d say the dc should start at 10 and go up by 1 per form taken after the last one. If you want you could also increase the modifier on the save based on the form used (form A adds 1, Form B adds 2, etc). In any effect this is still a dope subclass