Wolf in the Snow 

Stiles had thought he had defeated it. That it was no longer a worry. He was wrong. Now it's back, and he's not sure if he can defeat it again. The pack, however, refuse to let him quit. Sterek Derek/Stiles eventually wolf!Stiles
Keywords: stiles, stilinski, genim, derek, sterek, cancer, pack, wolf, werewolves, mates