Xerex, the Non-Euclidean World

—Once per turn, if you don't have a creature adventuring, choose a creature you control to adventure (it leaves the battlefield). Roll a d20:
• 1: Create a number of treasure tokens equal to
your creature's mana value!!
• 2-4: The adventure is done! (it returns tapped)
• 5-8: Put a +1/+1 counter on your creature!
{bull} 9-16: The adventure continues...
{bull} 17-19: Put -1/-1 counter on your creature...
{bull} 20: Y