Eliminate the Competition
Sorcery
As an additional cost to cast this spell, sacrifice X creatures.
Destroy X target creatures.
Open hostilities are strictly forbidden at the Inventors' Fair, but "accidents" still happen.
Joseph Meehan
Kaladesh Promos (PKLD)
• #78sRulings
If you somehow cast Eliminate the Competition without paying its mana cost, you'll still choose a value for X and sacrifice X creatures.
(wotc • 2016-09-20)
Once you announce that you're casting Eliminate the Competition, players can't try to remove creatures you'd like to sacrifice.
(wotc • 2016-09-20)
Rulings
If you somehow cast Eliminate the Competition without paying its mana cost, you'll still choose a value for X and sacrifice X creatures.
(wotc • 2016-09-20)
Once you announce that you're casting Eliminate the Competition, players can't try to remove creatures you'd like to sacrifice.
(wotc • 2016-09-20)