Used the Mystical Dagger from Forbidden and Arcanus on a bird from Exotic Birds and it crashed the server.
Easily repeatable.

Edit:
Tried it on a Minecraft Pig and it crashed as well, so guess it's unuseable.

Im updated to Forbidden and arcanus 16.2.3 and worked. So we only need the modpack Creator to link new Forbbidden and arcanus update @simibubi . Specially for MultiMc and other platforms that can upgrade automatically or download automatically