Portal of Anomalies

Cascade. Ward {3}.
At the beginning of your upkeep, remove Portal
of Anomalies from the game then return it back
to the battlefield before your next draw step.
Whenever Portal of Anomalies enters the battlefield and wasn't cast from your hand, roll a
D20 dice. If the roll is 6 or less, exile all creatures
on the battlefield and Portal of Anomalies.