Ashe's Posterus Sight

In a fraction of a moment you see perfectly into the near future. Roll two d20s for each creature you can see, up to twenty d20s, and record the numbers rolled. You may then assign any number of these numbers to any number of creatures you can see, up to ten creatures.

Anytime one of those creatures would make any attack roll, saving throw, or ability check, during the duration of this spell, you may choose to replace the roll with one of the numbers you had previously assigned to that creature. You must choose to do so before the roll. Each number can only be used once, and the spell ends when all of the numbers have been used.