[ano]

Seems like monsters and undead (and maybe demons as well) don not transform which is logical, IMO.
As for Bane Lord, giving him an amulet is a bad idea due to another reason: it is quite vulnerable overall and the best script for him in most cases is to wait for several turns and then attack closest to be out of range of most spells. I've had very bad experience with BL's wearing Lychantrop's amulet. Mages slay them really easy.