This deck is fun and surprisingly good - I only started playing it after trying a few very dubious decks and falling to rank 200 or so, but I've gained back about 100 ranks and others have had a similar experience.
Some notes on playing the deck:
1) Against aggressive decks you hope to buy enough time with Torch/Equivocate/Brenn to survive to your 4-drop plays with a healthy life total. The dream is of course T4 Stirring Sand -> Great-Kiln Titan (which is very hard for skycrag to beat), but also just sticking a SST is often enough against aggro. Stirring Sand and Mirror Image can function to some extent as extra copies of SST.
2) The matchup against midrange decks is similar (you mainly just want to avoid dying, since your deck will be favored in longer games), but against time-based midrange you care less about SST and more about your larger sentinels. (Having many copies of SST is still great against justice-based midrange decks, of course.) Equivocate is at its best here, and Brenn can do solid work with letting you start hardcasting big sentinels a little sooner. The hardest part of this matchup is knowing when to stop discarding your big sentinels and switch to the plan of hardcasting them all.
3) Against control decks you just want to hit power drops and hardcast all your threats. You usually don't want to discard your big sentinels here unless you are really getting flooded with them. Instead, discard excess Herald's Songs, Brenns, and Torches. If you don't get stuck on power, you are extremely likely to win once you start playing a HotV, GKT, Lavabloods, or Stirring Sand every turn; you just have too much threat density and card draw. You are highly favored here.
4) Brenn is an interesting card in this deck, but far from essential to the deck's functioning; don't focus on him too much when playing. Basically Brenn is a better Trail Maker in this deck - he blocks a bunch of units, doesn't die to Vara's Favor, and gives you 1-3 extra power each turn if he lives, which lets you play multiple spells in one turn or hardcast a sentinel 1-2 turns early. After the first 3-4 turns you almost always want to discard Brenn to Song/Observer/Strategize instead of playing him. Occasionally you'll do something busted with Brenn (e.g. I have had the start T2 Brenn, T3 Mirror Image, T4 spell + Heart of the Vault, T5 spell + Lavablood Goliath), but he's mostly just a solid early blocker that speeds up your deck a little.
5) Herald's Song is mainly in the deck to give you more T4 GKTs, but don't forget that it's also a great card to discard (or put back with Strategize). If you loot it away twice with Observer/Strategize, you are actually up a card in the transaction. Discarding one half of Herald's Song to the other half isn't as good, but it is still a play that often happens.
6) Your only explorer for Stirring Sand is Nocturnal Observer, but that's fine - bringing back one sentinel is still great value for the card and it provides a use for Observer later on when it is no longer night. In a longer game where you are hardcasting sentinels, you will sometimes want to spend 9 power to play Observer and 6-cost Stirring Sand in the same turn. Don't forget that you can't discard with Observer on the same turn that you use it for Stirring Sand.
7) You can often set up Great-Kiln Titan's ability by playing a crest in the same turn. If you don't know the top card of your deck then playing Great-Kiln Titan into an empty board is a little risky because you might hit Equivocate, but it can still be worth the risk.
8) Don't miss lethal - this deck has a bunch of burn between Torch, HotV, Lavablood Goliath, and ways to copy/rebuy Lavablood, so you can often win out of nowhere once the deck gets rolling.
9) The worst matchup for the deck is Praxis Tokens, since they kill you pretty quickly and you don't run Hailstorm because of Brenn and Observer. Madness decks (e.g. Felnscar Scream, Grenadins) are also pretty good against you. On the other hand, you are favored against Skycraggro and highly favored against most control decks and time-based midrange. Justice-based midrange and other aggro decks are generally close matchups.