Enemy Skill Materia

{4}, {t}: Roll a d20. Each opponent exiles cards
from the top of their library until they exile an
instant or sorcery card, then shuffles the rest
into their library. You may cast up to X instant
and/or sorcery spells from among cards exiled
this way without paying their mana costs.
1—9 | X is one.
10—19 | X is two.
20 | X is three.