Anyways b/c Bethesda's prologues are interminably long I use an alternate start, and of the alternate back-stories offered, "I've become a warlock's thrall" is one of my favorites. You start with a pretty powerful Ring of Resist Magic, and already equipped to boot...

...implying your master was too dense to recognize it for what it was, gave it to you to see what would happen, and accidentally broke his own Geas.