With Baubles and Blood Arsenal installed, any mob can not be hit. Simply go up to any mob (passive or hostile) and try to hit it.

Also, if I remove Baubles, it works fine. If I remove Blood Arsenal and leave Baubles, it also works fine.

Baubles-1.10.2-1.3.BETA11
BloodArsenal-1.10.2-2.0.1-13
BloodMagic-1.9.4-2.1.0-65
Guide-API-1.10.2-2.0.2-45

Forge version 2107

Very strange. Baubles does not even come close to modifying any code that would impact combat or do something you describe.

Yeah, maybe it's on Blood Arsenal's end. Can't find their issue tracker though. :/

There issue tracker is right here: https://github.com/Arcaratus/BloodArsenal :)