Piotr, Inventer of Math

X: Remove X homework counters or sacrifice X homework tokens, draw X cards, mill X cards or create X blue mana.
-X: Remove the top X cards of your library from the game face down. Every upkeep, you cast a random one if possible without paying it's mana cost.
-13: You get an emblem with "you may have two of the same legendary card on the board instead of one".