The Great RNG

This card can be your commander.
At the beginning of your upkeep, roll a
twenty side die, and activate one of the following abilities
• 20 = set all opponent life totals to zero
• 1 = set your own life total to zero
• 15 = opponents lose half of their life, rounded up
{bull} 5 = you lose half of their life, rounded up
{p/w}{p/u}{p/b}{p/r}{p/g}: reroll the dice