That 'making a deal with an elf and giving up your first born' thing with the human going 'Okay. When do we start?' but it's Sterek.
Alpha Derek who protects the woods and makes deals with the townspeople to protect them in exchange for their firstborn joining his pack and thus joining the protection of the town. It's how he got Boyd, Erica and Isaac (loophole of the firstborn already being dead) to be his Betas.
When Stiles comes to him, Derek is a little confused because Stiles is definitely too young to have a kid old enough to join the pack. But it's okay. Derek can be patient. He can tell Stiles is genuinely concerned for the town. But when the deal is truck...
Stiles: Okay, when do we start
Derek, confused: Start with what?
Stiles: I just promised you my firstborn. I don't have one yet. These take like nine months to be done. So we should start
Derek, even more confused: We should start
Derek, appalled: I would never force myself onto anyone--
Stiles, very deliberately looking Derek up and down: No force needed. Well, wouldn't mind a little manhandling
Derek, flustered for the first time in his life: ...















