Given how Polymorph currently works, that could be a pretty big debuff, in an off itself. The kind of thing low-hp/high damage builds (ergo, blood knight dependent melee, or mages) would be very vulnerable to. I like it. Edit: To keep the flavor, I also think it should apply the actual werediggle polymorph buff. That way, it's a hassle for everyone but those select few who've taken up the challenge of a werediggle centric playthrough.