The general style is to drop vehicles and artifacts while slamming into your opponents forces over and over
Hellkite Courser is particularly bonkers with The Ur-Dragon since its whenever one or more Dragons you control attack trigger is amazingly powerful, as befitting a nine-mana Dragon Avatar
For six mana, you get an uncounterable, evasive and hasty creature that is sure to demand an answer the second it enters play
It still wont always line up that way, as sometimes your opponent has small stuff too, but Expel does make it possible for you to make this feel more one-sided, and that makes it quite powerful, especially because it still effectively has the usual Wrath upside of just nuking the whole board This has somewhat passable stats, and it has an ability that is useful, albeit expensive
I would put solid money on these cards becoming valuable parts of a collection in years to come