Complex sentence: Warlocks in Dungeons & Dragons receive their powers through the influence of some powerful being, typically a Demon or Fey and are either born with these powers or receive them through a fell pact, which turns their soul into a dark font of eldritch powers.
Split into simpler sentences: Warlocks in Dungeons & Dragons receive their abilities through the influence of some unearthly being such as a Demon or Fey. They are either born with these powers or receive them through a fell pact, which turns their soul into a dark font of eldritch powers.