Activate Wall of Blood by paying 1 life, giving it +1/+1 until end of turn.
Repeat step 1 until you have paid an amount of life equal to half the highest life total among your opponents, rounded up.
Activate Rowan by tapping it, reducing the cost of all black and/or red spells you cast this turn.
Cast Debt to the Deathless, choosing for X to equal the amount of life you've lost this turn, but paying a total of ({W} magic symbol) ({W} magic symbol) ({B} magic symbol) ({B} magic symbol) due to Rowan's ability.
Resolve Debt to the Deathless, causing each opponent to lose twice X life, and you to gain life equal to the life lost this way.
Each opponent loses the game due to having 0 or less life.