Let the Galaxy Burn [Warhammer 40,000]

Set: Warhammer 40,000 Type: Sorcery Rarity: Rare Cost: {X}{5}{R} Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom of your library in a random order.)Let the Galaxy Burn deals X plus 2 damage to each creature that didn't enter the battlefield this turn.