Endra, Champion of Shavka immediately stood out to me a cool card with high potential from Promises by Firelight. I considered a few shells: Skycrag spell damage and FTP copy shenanigans, but I ended up going with a void recursion focus, and it's been working well.
The deck is hard focused on Endra, with heavy draw and very few parts not intended to synergize with her. The deck moves fast, cycling heavily and really popping off with the extra mana that later Shavka plays start getting you. I decided to also include
Kuro, Champion of Makkar for the useful void draw, and for the fun of having two champions in the same list. He's performing slightly worse than Endra, so your mileage may vary.
Cozin Darkheart is not directly tied to the main game plan, but her mastery is easy to activate with the weapons in the list. She's good to have around for situations where you don't have Endra available, and for something to dump on the board regardless of other cards.
The market cards are a place for personal choice. Removal choices may vary, I've considered adding Dizo's Office but decided against it in favor of a faster play style. I usually like power in the market, but in such a cycle-heavy power generating deck, I don't think it's necessary.
The deck is performing well and has so far taken me to Diamond 3 with a 63% winrate (and some of that was an earlier build with less optimal card choices). I don't doubt it can do Masters, and it's very fun to play! I may change cards but the deck as it stands is succesful and highly recommended.
I think i'd consider swaping out the Kuro for something though. Maybe baby Vara to get rid of the aegis which block Endra?
Ripknife Assassins do really well too, as blockers for things too big for endra's ping, or if board clear to buff the cozin/endra/dredgers. Maybe swap half the sporefolk for them?