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.
Deathbringer Regent's last ability destroys all creatures except Deathbringer Regent, including the five other creatures required for the ability to have an effect.
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).