One

There are two types of demons in the world.

Natural born.

Fallen angels.

Both are equally frightening, but let humans live their lives without harm. Except for certain instances.

In exchange for peace, certain demon lords reign over provinces. Their rule is fair and just as long as their one need is met.

A pet of their choosing.

A lord can choose whomever, and however many he wants.

Most pets live peaceful, even lavish lives under their demon masters.

The worst is when their wings are shown. A demon's wings are proof of its power and superiority. They only show when the demon wants them too.

Save for when they are aroused.