Looming Calamity

As an additional cost to cast Looming Calamity, secretly choose a number between 1 and 10.
When you cast Looming Calamity, each opponent guesses a number between 1 and 10. If the
number chosen to cast Looming Calamity is
guessed, counter Looming Calamity.
Looming Calamity deals 10 damage to each
creature, each planeswalker, and each opponent.