Starfield of Nyx is a huge reward for playing a enchantments. First, you’re getting a potential Opalescence effect. With enough enchantments in play, yourother non-Auras will come alive and start getting in for big chunks of damage. The more common usage, and what will be important when building up to these big attacks, is returning an enchantment from your graveyard to the battlefield each turn. If you're using enchantments as removal spells or can find ways to put enchantments into your graveyard, this will yield insane value.
Sigil of the Empty Throne is the other win-con for a deck filled with enchantments. With enough cheap enchantments, you’re going to be able to crank out a battlefield of Angels to defend yourself before turning the corner. Playing more expensive enchantments to bring back with Starfield of Nyx is also viable.
Vessel of Nascency and Oath of Jace weren’t quite there in Starfield of Nyx's time. They'll load up your graveyard while helping to find important pieces. The Starfield of Nyx will eventually get these enchantments where you want them and onto the battlefield.
The only creatures in this deck outside of what Starfield of Nyx and Sigil will eventually produce are Elvish Mystics and Herald of the Pantheon. These will make sure you can cast your big enchantments and that you have the mana to dig deep early.
There are tons of white enchantments that will help neutralize opposing threats. Isolation Zone, Oppressive Rays, Silkwrap, Stasis Snare, and Suspension Field will all take care of creatures and other threats. Outside of the Rays, none of them are Auras, so you’ll be able to attack with them when the Starfield is active. Quarantine Field doesn’t return from the graveyard quite as gracefully as the others, but it will help take care of threats you might not be able to deal with.
Myth Realized is an interesting card that hasn’t really seen the play you would expect after so much hype. A 1-mana enchantment is a nice way to trigger Sigil, or to get enough enchantments in play to turn on Starfield. It also can come down early in the game, load up on counters, and offer a formidable threat.
Lunar Force represents a soft lock in conjunction with Starfield of Nyx, forcing your opponent to play a test spell into the Lunar Force before they can cast anything of relevance. When you’re already getting the sick value of a free enchantment every turn, making your opponent play multiple spells just to resolve something tends to be the nail in the coffin!
With mana acceleration, lots of cheap spells, and an end game that can go over the top of pretty much anybody, Bant Starfield is a pretty sweet deck to explore in the new Frontier.