Complex sentence: Sam is killed by the super-strong Jake Talley, but Dean sells his own soul to a Crossroads Demon in exchange for Sam's resurrection, a contract that leaves Dean with only a year to live.
Split into simpler sentences: Sam is killed by the super-strong Jake Talley, but Dean sells his own soul to a Crossroads Demon in exchange for Sam's resurrection. The contract leaves Dean with only a year to live.