Demons are Divines who choose to rebel against the last wishes of the Three Mothers.
As signs of their rebellion, they were stained with dark energies, and many were given fearsome forms in order to warn unknowing mortals of their betrayal.
However, despite their condition, not all demons are particularly evil or mean ill for lambkind.
Many of them, simply wish to exist independently from mortals but struggle with the fact that it is not possible to do so without relying on them.
And so demons will tend to make more impactful contracts with mortals and in exchange offer even greater power than their non-demonic brethern.
In order to accept a relationship or contract with a human, demons require a great sacrifice in return.