Feln Sacrifice Broker

EDIT
I realized that this deck needed even more removal, so I added 3x Permafrost for soft removal. The Nesting Ravens aren't really good for late game and 4 was overkill, so I took out 1 of them. I also removed one Two-Face and one Feartracker. I also removed the Plagued Griffyn and replaced it with Colony Matron, both to provide more blockers/sacrifice fodder and to provide Lifesteal.

Market:

Polymorph is used to remove units that are monstrously large or have a troubling ability.
Innate Conviction is here for removing weak units and also to create a 3/5 flyer with berserk and spell damage +2. Innate conviction itself can become a win con if you have enough spell damage to finish off your opponent.
Linrei's Stranger is really good if you are playing against a slower deck and are leading. Getting Linrei's Stranger onto the board will allow you to easily overwhelm your opponent, as well as create flyers- working well to create board advantage as well as working with Highsky Lookout. This is really niche though- Linrei is mainly for attacking but may help with your invoke, otherwise.
Mysterious Waystone is the default win con of the deck. I mainly use it because it's fun- working off of Nesting Raven, the shade forms of Two-Face, Highsky Lookout, Plagued Gryffyn, and Feartracker. It also functions well off of Flamebathe Reformation.
Black-Sky Harbinger is good against swarm opponents, such as opponents with 1/1 Grenadins or 1/1 Cultists. It also allows for lifesteal/flying damage. It also breaks Aegis.

Main Deck:

Nesting Raven is primarily used as a blocker. It may be tempting to turn the raven into a 1/1 flyer, but it usually is best to keep it as a 0/4 and to remove units with Annihilate, Lightning Strike, Biting Winds, or Deathstrike. I suggest keeping the raven as a 0/4 until either you have a Highsky Lookout in hand or if you have a Mysterious Waystone. Eilyn's Favor as well as Wisdom of the Elders are there to thin your deck out and to provide a little ramp/card draw. Two-Face is deadly and breaks the opponent's Aegis if they have one. Plagued Griffyn allows some passive damage (recommend to target whichever unit deals the least damage to you/can be blocked without it dying) and it also serves as a 1/5 blocker, including sacrifice fodder. Feartracker is just great as a 5/4 unit, but she also breaks Aegis as well as keep you alive. She also provides sacrifice fodder. The Amethyst Monument is very important as it provides you with 4/4 Pumas with Lifesteal. Sacrificing the puma onto a flyer with Flamebathe Reformation will give you a flyer with lifesteal Flamebathe Reformation is also useful for just making units bigger/flyers in general.

Optional
For more consistency, consider removing some or all of the Cobalt Waystone and replacing with Feln Vow. (You may want to redistribute the power curve if you do this). The life loss should be mitigated because of your Lifesteal and Cobalt Waystone doesn't add much value since Eilyn's Favor is already in the deck. Alternatively, replacing Eilyn's Favor with Seek Power will also work, but doing so will cost you an Aegis effect.

Additionally, if you want to have more fun with Flamebathe Reformation, you can swap out Polymorph, Linrei's Stranger, or Black-Sky Harbinger from your Market for Madness. If going this route and you want to cheapen the deck a little, I suggest swapping out the Black-Sky Harbinger as this deck already has plenty of Lifesteal and the harbinger fits in really niche situations (as stated above).

Tips
Generally, if a weak unit with 1 or 2 attack is hitting you, it's better to brave the damage and save your removal. You will likely make up the lifeloss with Lifesteal later on.
Use Flamebathe Reformation on your stunned/soft removed units. Sacrifice them and give their stats away to units that can attack. Additionally, Flamebathe Refromation is best used on units that just enter the field and can't attack yet. Take their stats and give it to something that can attack! While you can create 1 massively big unit and ram your way through the opponent, I do not recommend this. Boost your units up evenly so as to avoid putting all your eggs into one basket. Don't attack unless it's safe/you have a considerable board.
Colony Matron is very useful as she can generate one 1/1 flyer with lifesteal per turn and it can be used as a blocker or as sacrifice fodder via Flamebathe Reformation to give something else flying and lifesteal. She helps you while your still setting up the board, but then turns into a ferocious threat and you either swarm the opponent, or have big flyer/lifesteal units!