Chaos Emperor Dragon - Envoy of the End
This card can only be Special Summoned by removing 1 LIGHT and 1 DARK monster in your Graveyard from play. Pay 1000 of your Life Points to send all cards in both players' hands and on the field to the Graveyard. Inflict 300 points of damage to your opponent's Life Points for each card that is sent to the Graveyard by this effect.
Alongside the priority rule, this card couldn't be stopped without a stupidly situational counter.