Mox Gambler

At the beginning of each upkeep roll a 20 sided
die. Mox Gambler's power and toughness are
equal to that value.
{t}: You may counter target spell if you roll a
value equal to or less than that spells converted
mana cost on a 20 sised die. If you roll higher
you lose life equal to the value. Do this any time
you could cast an instant.