It also massively improves your first combat by giving your creatures first strike and untapping them, which allows for much safer and potent aggressive plays
Dracogenesis (Showcase - Halo Foil) - $150.74 The kind of enchantment that can spell doom for opponents, Dracogenesis lets you play Dragon spells without paying a mana cost
I played this card, by the way, at the draft we played when the cards first came in (yes, we get excited when we get the cards too it just happens earlier for us) and it was a beating
In addition to taxing each of your opponents' spells by one mana, slowing them down significantly, Grand Arbiter Augustin IV provides you with a significant mana discount on your blue and white spells, respectively, providing an even greater cost reduction to Azorius spells
The broader target range and better late game scaling make Oust the better control card but both are good enough that you will play either in either if you just need more removal
Not only that, but it can trigger multiple times per turn just by casting non-creature spells