I've seen many lists without
Reconnaissance. This is such a strong card in this deck. It lets
Kaalia of the Vast be a little more safe attacking into opponents with fliers, but it also gives "pseudo vigilance" because you can untap your attackers after the combat damage is dealt. This is super valuable because your huge demons dragons and angels make for intimidating blockers, but are commonly tapped.
Scourge of Kher Ridges is super strong. A repeatable board wipe for little guys that doesn't affect you (because pretty much all the creatures in the deck fly) is super strong. Kill all their dorks!
Archon of Emeria it's really common to only play 1 spell in your turn anyway as most of your board state is coming from slams. And this will definitely have an effect on your opponents. I think some of the enchantments with the same effect would also be very effective (ex:Rule of Law). The advantage of the Archon is that he fits with other aspects of the deck. He's a flyer that can help block or get in some damage (which can be significant if some of the doubling effects are in play).
Drakuseth, Maw of Flames is one of the few beaters that doesn't do something the turn he comes out (aside from hitting for 7). But when he starts attacking... the 3-4 damage hits he does is commonly enough to just kill everyone else's commander (generally unless they're running voltron type decks). Killing everyone's commander every turn is extremely oppressive. And if that's not happening, he's killing other critical creature board state, or simply just doing a ton of damage (another good target for lifelink).
For Sire Of Insanity, the goal here would be that your board state is good enough to win if it just sticks around. So you just clear out peoples ability to change it. You could swap this one out if you don't like the effect.
Armageddon is similar. It's land destruction, so take it out if your pod hates that, but if you can get this to go off with good board state (which can be as simple as Kaalia of the Vast being out, with good slam options in hand), it can really secure a victory.
Vault of the Archangel is there for lifelink. Some of the "pain for draw" options (Vilis, Broker of Blood, Necropotence, etc) can leave you low on life. Triggering this a single time with a few guys out will give you all the life you need for the entire game. The drawback is the land doesn't tap for color.
Liliana's Contract I view this as a 5 cost for 4 draw. Nice juicy draw, that's all. If you've got Razaketh, the Foulblooded out and another demon or two, you could consider tutoring to favor demons to try to complete the set. But really the card is there simply for the draw. Compare it to Harmonize.
For Settle the Wreckage, it's not that uncommon to have 4 mana untapped for responses in this deck because you don't need to cast much to build horrifying board state. And this card can completely change a game when someone is trying to close it out.
I do not see Embercleave in many Kaalia of the Vast decks. But this card always feels good when I play it. It's extremely common to play it for either just the or sometimes an extra colorless. The double strike can seriously amplify the damage coming from the creature you put it on, but also the instant nature of this equipment can let you put it on one of your creatures that was blocked giving it surprise trample. Consider this hypothetical (I'll use specific cards in the example, but this generalizes to a lot of possible creature options and occurs relatively frequently): you've got out Kaalia of the Vast and Avacyn, Angel of Hope. You move to combat and no one removes Kaalia of the Vast. You attack and slam down Gisela, Blade of Goldnight. A scary hit for 30 coming towards your opponent (thanks to the doubling effect from Gisela). They opt to block Avacyn, Angel of Hope with some throw-away creature (maybe they've got a bird token siting around from a spell previously countered by Swan Song) because they are afraid of the hit. This would reduce the damage taken to 14... which might let them survive... but you laugh and for 3 cast Embercleave at instant speed and put it on Avacyn, Angel of Hope before damage resolves. Now they're looking at getting hit for ((9 * 2 * 2) - 2 + (5 * 2) + (2 * 2)), a horrifying 48. And the sword sticks around too! Feels good every time.
Sword of Fire and Ice provides protection from red/blue. That's helpful for common removal like Pongify or Rapid Hybridization. This can also be helpful for allowing Kaalia of the Vast so slip through, unable to be blocked. The 2 damage ping is useful for killing small critical creatures and the draw is just generically good.
Notable Exclusions
Master of Cruelties - this card can 1-hit someone who has no blockers. But after the first attack, he doesn't do much. I find commonly people will have at least a dork that can block. Arguably worth it for the small chance it works out, but I find it more threatening to the overall table to get out a gift that keeps on giving like Gisela, Blade of Goldnight or Razaketh, the Foulblooded. Also, the 1-hit is generally more effective early on in the game... personally, I don't really like killing someone on turn 4, only to not really threaten anyone else afterward. Could have a place, depending on your style.
Kaalia, Zenith Seeker - expected draw is roughly .25 * 6 = 1.5. 3 for 1.5 draw doesn't seem good enough.
Reya Dawnbringer - Powerful ability, but I find the ones that are impactful immediately are more useful. Not uncommon to lose her before the next turn starts. Plus it can whiff if you don't have stuff in the graveyard yet and she's what you have to slam.
Lord of the Void - I ran him for a long time. Whiffs a lot. I think this depends a lot on what decks you're fighting against. If someone is playing a deck with lots of big creatures, sideboard him in.
Boros Charm - Not as good as Teferi's Protection or Flawless Maneuver. If your pod runs a ton of board wipes (also: destruction board wipes, as this won't help with Cyclonic Rift or Toxic Deluge, which are super strong and common), you could put it in. The double strike can be handy as well.
Terror of the Peaks - Great card. Just not impactful the turn it is slammed. Also, part of his appeal is that he's only 5cmc. For us, because we're slamming guys, we don't care about the CMC. Sure, he's 5cmc and Avacyn, Angel of Hope is 8. But for us, the difficulty to get them out is the same.
Akroma, Angel of Wrath - She's scary, but she doesn't change the battlefield. She'll stick around and do some damage, but no one's heart is going to sink when she lands like they will for Avacyn, Angel of Hope, or Balefire Dragon.
