To meet the companion requirement, they forgo running any creatures, which is especially common in Pioneer
This five mana Black and Red 1/4 with first strike and deathtouch is great in a fight, but even better if you can make sure they dont get blocked
Whenever you roll Chaos, create a 7/7 colorless Eldrazi creature token with annihilator 1
When Veiled Ascension or another face-down creature comes into play, you get to pit a flying counter on them
It offers you a bit of defense by stunning an opposing creature when you get attacked, and with proliferate, its not untapping any time soon
They also have dedicated land support with Haven of the Spirit Dragon, Crucible of the Spirit Dragon, and Temple of the Dragon Queen, making it easy to support a 5-color dragon deck