David, King of the Random

Whenever you roll a d20, if you roll a 10 or higher, choose one of the following effects matching with
the phase.
Untap: Tap all of target opponent's artifacts.
Upkeep: Trigger all upkeep triggers.
Draw: Target player draws a card at random.
First Main: Tap 5 creatures at random.
Combat: All creatures block this turn if able.
Second main: Untap 5 creatures at random.
End: Trigger all end step triggers.