In fact Angels can be worse than demons, there was one case when a peson was nealry killed by an Angel , and was never harmed by a Demon.
Even if you in fact knew how to summon Angels and Demon which is a extrenmelly restricted ritual you wont find it in any bookstore, angels hate humans , they call us fluid Bags , since they are pure energy. Just to Illustrate what can happen to you if you mess with this , Angels can drain all your life force in an instant , only to kill you , not because they need that deleteric energy because they dont , they drain it and disperse in the enviromment for fun. They dont like to be called and disturbed specially by us.