Death Dragon is a family that debuted in SD34. They're generally Purple and their family's namesake likely comes from how their effects have a tie with the "When Destroyed/Depleted by the Opponent" timing. In Battle Spirits Double Drive, they're used by Tatsumi.
In the God-King Saga universe, they were the first group to find the Imagine braves. Their team is named "Team Turon" and their God-King is Ourovorius.