Bernice Summerfield: Goddess, what's happened to Annie?
Mary Hughes: Her eyes! Look at her eyes!
It is the nature of magic to unpick reality, and so the daemon, a conscious personification of magic, cannot prevent its warping effect on its newly acquired mortal shell. Gradually the body will mutate, twisting into a grim distortion of its former shape. This is a never ending process and it is only a matter of time until the daemon's presence becomes apparent by the mutation of its host's body.
His face suddenly ran together like melting wax, the eyes flattening and spreading like knife-struck egg yolks, nose widening and yawning, mouth disappearing. The head elongated, and the hair was suddenly not hair but straggling, twitching growths.
The slow, cavernous sound came from what had been his nose, but the nose was eating into the lower half of his face, nostrils meeting and merging into a central blackness like a huge, shouting mouth. Robert got up, still chuckling, and behind it all she could see the last shattered remains of the other Robert, the real little boy this alien thing had usurped, howling in manic terror, screaming to be let out.
Banes are Umbral horrors, and are not used to the concepts of biology and physiology that govern the human body. They almost find the human form weak and - perhaps - even a little grotesque. So they change it. Again, the host doesn't get any comfort in this process. He feels, perhaps painfully, perhaps not, what the Bane is doing to him. If the Bane needs him to develop glands through which to secret poison or webbing, those glads appear - and the host must wait in terror as new organs form in his body. If the Bane feels that "it's" human needs another set of eyes, the host must cope with itching, then pain, the suddenly seeing from another perspective.
—Werewolf: The Apocalypse - Possessed: A Player's Guide