Ushri's Vow

Ushri's Vow deals damage to each tapped creature equal to the number of times you've cast a commander from the command zone this game, you gain that much life.
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"Come then all you gods, spirirts, demons, and any other half wit who claims to be a warrior. I'll show you why this mortal has earned the name oni." - Ushri, Templebound Oni