Oswald, Master of Chance

At the beginning of your turn, if Oswald, Master of Chance is in your hand, roll a d20. Oswald, Master of Chance mana cost is X colorless mana, where X is the roll on the d20.
Roll a d20. Oswald's power and toughness are equal to what you roll.
{t}: Roll a d20, if you roll a 20, take control of target permanent.
{5}: Reroll one dice.