Mizzium Gauntlet

{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.