Back in an old campaign we ran in FR, I'm running a LE fighter/mercenary, we ran into the Mistmaster and had a series of "episodes" with the DM taking us out of the room and giving us visions and soforth. When it gets to my character's turn, he's face-to-face with a Baneare offering him the whole deal (power and suchforth) at a later point. I turn it down, having some loyalty to my employers (the party) at this point.
Cut to later. We run across a dragon. I try to appeal to its greed, talk it off. Party mage M.M.'s the thing. I'm shish-kebabed inside of a round then resurrected as a brown bear. First night, I'm on guard, the Baneare appears to me again. I'm a bit more willing this time. She gives me the ability to transform between human and bear by placing this crystal spider inside me. I stay as a bear until we get back to town, where I make up a story about buying a wish that lets me turn. Nothing else is asked of me until one session when we are confronted with the queen of the Silver Marches. The little spider leaps out, and Soul Traps Aulustriel. Rest of the party looks on in shock at the fact that I had been a traitor for such a long time.