The Ballad of Khantsievth

For each {b} in a cost, you may pay 2 life rather
than pay that mana as long as you control
another Demigod, Demon, or God.
Whenever a Demigod, Demon, or God you
control becomes blocked by another creature,
that creature's controller sacrifices a permanent.
"Ever, ever, marching on
The Six will face their fate."