I didn't think I'd be able to do the necessary research to post here--I take my fanfic very seriously indeed (g)-- but you mentioned Tree's "Alchemy" and I remembered this:

"You. You're mine. They gave you to me and I'm not giving you back. I don't quite know what to do with you, but I'm not giving you back."

Mulder's inner voice being territorial. I quite like territorial.