Besniat, The Mad Sorcerer

Wild Magic Surge—Whenever Besniat attacks
roll a d20
1-9 Draw a Card.
10-19 Search for a Sorcery or an Instant
in your librart and add it to your hand,
then shuffle.
20 All spells change their color, alongside
their mana costs to any color of your choice
until the end of your next turn.