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.

Warlocks get their power from making a pact with a powerful being.

Warlocks get their magic from powerful entities that they enter into a contract with. This pact may not be fully known to the warlock.

Typically, warlocks serve dark masters and will have a mission or goal. If they don’t serve the entity well, they will be punished or in extreme cases killed. Serve well, and you will likely get gifts.

Warlocks tend to have limited magical abilities compare to other magic users, but their abilities “hit harder” as warlock spell splots are limited to the current warlock level.

Other magic users get level 1 spell slots, then level 2, etc.

Warlocks get all level 1s, then all level 2s, etc