Garfield, the Deals Warlock

Each player rolls a d20 on their upkeep. If a player rolls 10 or lower on a roll triggered
this way, artifacts that player casts cost {1} more to cast until end of turn.
"Prepare to contest me, Garfield, the Deals Warlock, in a test of mercantile wits!"
—Garfield, the Deals Warlock