The Sellsword

You are a Renegade (You have a unique win condition)
Teammates win together. You win alone.
When a source an opponent controls causes
you to lose life, if the Sellsword is face down,
flip it face up. When you do, your opponents
bid life. The player that caused you to lose life
starts the bidding with a bid of 0 life. Players
may not bid more than half of their life total.
The highest bidder loses life equal to their
bid, then you become their teammate.