Bazaar, The Tower, The Last City, Earth

The Guardian gives the Drifter a Seething Heart which was obtained from killing an Ascendant Primeval Servitor in Gambit.

The Drifter: What. Is. This? The heart of an Ascendant Primeval. I'll take that, thank you very much. We'll use it later. While I have you here… Get this: a while back this punk stole something… important to me. Thing is, he's like us - ever-living till you get his Ghost. But seeing as I ain't laid eyes on him in something like forever, guessing his Ghost probably got… got. So do me a favor and, uh, go see if that punk has what's mine, huh? I'd do it myself, but as you can see, I'm a busy man. Besides, you're the closest thing to reliable I've met in a century.