Death Transference

When Death Transference enters the battlefield, lose half your starting life total. Target opponent gains life equal to the life you lost.
If you would lose the game due to an opponent's card, (whether by damage, or an ability that causes you to lose the game, or an ability that causes a player to win the game) you win the game instead.
During each player's upkeep, any player may pay {7}. If they do, exile Death Transference