G/W control deck that's tuned for coping with most of the more aggressive builds going around Arena. Dawn of Hope is the all-star here, providing chump blockers, card draw, life gain, and a win condition if necessary. Karn shines here as well, with enough incidental artifacts to give his constructs some teeth, but he's mostly another draw engine. Gaea's Blessing keeps you from decking, and including a couple copies incidentally beats mill decks. I've been tuning a prison deck for while, including mono-white, U/W, and Bant versions. Mono-white's anti-decking card is sanguine sacrement, but it's overall far weaker than Gaea's Blessing or Devious Cover-Up. Adding blue allows for some countermagic, but I've found it's unnecessary against most decks, the exception being Dimir discard/control builds -- while that matchup is bad for this build, it's not unwinnable, so long as you can get the Fountain/Dawn of Hope engine online early.
Tips: Multiple copies of Dawn of Hope are rarely valuable, and can often lead to a dozen or more triggers to click through, but it can be useful to drop a second copy if you only have one fountain out in order to get multiple draw triggers off that one life gain.
Against Izzet drakes, make sure to save a copy of Ixalan's Binding or at least Conclave tribunal for Niv-Mizzet.
Against G/B, the same is true for Vivien Reid, and to a lesser extent Vraska. No matter how tempting it is to use a Binding against Jadelight Rangers and other value creatures, they can be kept on a Root Snare lock until a board sweeper comes up, but the Planeswalker can come down and kill your other bindings, giving them even more value.
Don't overcommit to drawing as many cards as possible. It never hurts to toss a few soldiers in the way of incoming attackers in order to buy a few turns, and a misspent root snare can cost you a game.
Finally, don't worry if your Karn or Carnage Tyrants get destroyed, as they likely won't be gone forever with Gaea's Blessing recurssion. Carnage Tyrant is really only around to waste the opponent's time and slow them down, as he's unnecessary to winning (though he can speed matches up significantly).
This deck wins through inevitability, often earning a rage-quit from the opponent after they realize you're drawing 3-7 cards each turn while sitting behind a wall of invulnerability at 60+ life and they will deck before they can get a threat to stick. I'm considering dropping Karn for a couple copies of Immortal Sun, but I'm out of Mythic Wildcards. Give it a whirl and let me know what you think!
