In theory, someone using the true keys provided from the qaballah could learn to shapeshift, and this was one mark of high level merkaba mystics. The infinite secret negative can't be disproved, but, i am a religious scholar and a world religions scholar and i see and know of no evidence to suggest that they are modernly capable of this, and would certainly not beleive in any case that magick can be used for dark purposes. True high magick utilizes The will of god and thus cannot go against divine will. This may enabale a merkaba mystic to shapeshift, but all powers would be instantly lost the moment a merkaba mystic incurred even minor negative karma. Bad Jedi make for good movies, but

are not supported by real metaphysics. Demons are in most senses not even a tenth as powerful as even the weakest human. However, people can give their power to darkness;

but that only makes them weaker not strong. Sidhis derive

from attention to virtues, no exploration of vice.