In the roiling depths of the Eye of Terror, the bloodthirsty hordes of Chaos Marines plot the downfall of their loyalist brethren.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

"Holy places are no longer sanctuary from death, and death is no longer sanctuary from anything."
—Thalia, Knight-Cathar

Duskmourn: House of Horror Commander

In the early days of Valley, desperate animalfolk harnessed the power of Calamity Beasts in ways that destroyed more than defended.

Bloomburrow Commander

Everyone knew the bombs were coming. Everyone but the public.

Fallout

Although players may respond to Blasphemous Act once it's been cast, once it's announced, they can't respond before the cost is calculated and paid.

Blasphemous Act's ability can't reduce the total cost to cast the spell below {R}.

The total cost to cast Blasphemous Act is locked in before you pay that cost. For example, if there are three creatures on the battlefield, including one you can sacrifice to add {C}, the total cost of Blasphemous Act is {5}{R}. Then you can sacrifice the creature when you activate mana abilities just before paying the cost.

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Blasphemous Act). The mana value of the spell is determined only by its mana cost, no matter what the total cost to cast the spell was.