D&D 5e (a kind of Pen and paper RPG) has a magic class that the source of their power is basically an I-O-U (I owe you) with a powerful entity, usually their patron.

It is not straight away clear what their patron wants, but it tends to be ominous, they might receive a "gift" now and then, or they may even be punished.

In any case, I find it funny that all the other classes put the work to learn magic, while warlocks just went to ask the worst guy in the neighborhood.