The 20 Sided Die

When The 20 Sided Die enters the field, create a
D20 token. This token must be represented by a
20-sided die.
Whenever a creature attacks, the attacking
creature's controller may roll the D20 and give
the creature the corresponding affect.
Any player may Roll the D20.
• 20: Doublestrike, Unblockable
• 2-19: Nothing.
• 1: -20/-0.