Deathbringer Regent
Oracle Text
Flying
When Deathbringer Regent enters the battlefield, if you cast it from your hand and there are five or more other creatures on the battlefield, destroy all other creatures.
Card Rulings
2/25/2015 If you cast a creature spell that enters the battlefield as a copy of Deathbringer Regent, the enters-the-battlefield ability will trigger (assuming the “five or more other creatures” requirement is also met).
2/25/2015 Deathbringer Regent’s last ability destroys all creatures except Deathbringer Regent, including the five other creatures required for the ability to have an effect.
hopefully we will see some support for things like this. at least it costs less than Reaver Demon.