My Take on Limited Resources' Ixalan Rare and Mythic Rare Set Review

Continuing from My Take on Limited Resources' Ixalan Common and Uncommon Set Review, here are my nitpicky takes on their Rare and Mythic Rare Set Review.

• Ashes of the Abhorrent -- Given an F, and the first ability was said to literally do nothing. I was curious how many cards in the format it actually interacts with. I took a pass of the full set and there are two cards affected: Deathless Ancient & Repeating Barrage. I'm certainly comfortable with an F at that level of narrowness, but if you ever face a deck that somehow has two copies of those cards, or grindy control mirrors where one of those cards is known and your deck is unequipped to permanently deal with it in any other way, it's a conceivable hyperniche sideboard option to deal with part of those cards.
• Axis of Mortality -- The synergy with the two uncommon white vampires, particularly Glorifier of Dusk, was missed. Cast Axis, then with the trigger on the stack, make the Glorifier fly a bunch of times and threaten a lethal attack with it. Now, I don't think this brings the card into the good range, but I think it's a bad maindeck playable for decks with Glorifier. Particularly in lifelink mirrors, this combo could pull some weight. The normal use of the card will usually be a nonzero-value backup plan. Especially if our deck is slower in the matchup and we're likely to fall behind early before stabilizing, the Axis might conceivably be a good 6-drop in some game paths. Overall this looks firmly in the range of bad niche playable and I'd give it a Build-Around D.
• Legion's Landing -- Given a C+ for reasons I don't disagree with, but my gut is just a little higher. I think the value of the flipped land feels well-positioned in a combat-centric format and can take over a game to the extent where going out of one's way to flip it could be worthwhile sometimes. I'm at B-.
• Priest of the Wakening Sun -- This was given a Sideboard D. It's clearly at least a bad maindeck playable in many white decks, and I think the sideboard value is a bit higher. If it hits on turn 1 and triggers several times, it can pass the threshold of meaningful life gain, all while retaining the optionality of trading for an X/1 or cashing it in later for a card. I'm at C- overall, ideally mostly as a sideboard option (but I think it outperforms D out of the sideboard).
• Wakening Sun's Avatar -- Given a flat D. I think build-around C+/B- is far more accurate. LR throws around the build-around designation for far less, and this is clearly an impactful 8-drop in a format where a W/G deck might consider ramping to 8.
• Sanguine Sacrament -- Given an F, but I could see it playing two niche sideboard roles, admittedly at the Sideboard D level: (1) a midrange or controlling deck that can reliably almost fully lock down the board except for opposing slow reach elements (e.g. Lightning-Rig Crew) or (2) a midrange or controlling pure board stall mirror where decking with this is viable. These will depend greatly on the specific cards in the matchup, rather than just being a generalization to be made about archetypes or color pairs.
• Arcane Adaptation -- Given an F. For completeness, I looked at the tribal payoffs and... yeah, nothing is even close to being even a 0.1% niche application for this card. F!
• Dreamcaller Siren -- Marshall gave it a B and Luis an A-. My gut is definitely B. This doesn't block very many creatures in the format at all. Look at all of the fliers; Dreamcaller Siren trumps the few smaller fliers but trades off with Pterodon Knight, Wind Strider, Imperial Aerosaur, and is outright trumped by Shining Aerosaur, Air Elemental, Deathless Ancient, Glorifier of Dusk. The contextual size matchups make this a solid chunk weaker in a game where its caster is behind.
• Herald of Secret Streams -- They gave this a Build-Around B, but I think the ceiling is lower. This format feels like it devolves to creature races often, possibly even moreso with a U/G Merfolk deck, and unblockability is less critical in those cases, and that's where this card falls the most short of expectations. There aren't too many ways to make this grant unblockability to multiple creatures beyond River Heralds' Boon, Shapers of Nature, and Vineshaper Mystic, and if it's only giving ~1 creature unblockability, I don't think the average payoff for Herald is at the B level with the base rate on the body being so poor. I just finished a draft with 2x Herald and 4x River Heralds' Boon and I was still not impressed by the Herald. I think this card is closer to a Build-Around C+.
• Search for Azcanta -- This was given a flat D on the basis of a permanent Scry 1 every turn for two mana was not worth a card. I'm higher on the front side. I think two mana is about the right rate and that it should generate a card's worth of value, at least at the level of a weak playable. The flip side is some upside, at least in certain decks in slower matchups. I'd give this a C- and expect it to be even better in some matchups. LR went on to give Arguel's Blood Fast a  Sideboard C grade for use in control mirrors and from that perspective, I think this card is even better. 
• Sword-Point Diplomacy -- Marshall gave it a showy F and LSV a D. The F is clearly wrong, and a bad Browbeat should be a weak playable in aggressive decks. Worth noting here that consensus is emerging around this format feeling like one that's low on solid playables, so bad playables will happen more often. I'm on D.
• Captivating Crew -- Consensus seems to be that this is among the top cards in the set, so I was surprised that Marshall started it at B+ noting that it was clunky in his experience. LSV had it at A and they settled on A-. I can't imagine this card being worse than A- and my gut is with the masses that it looks like one of the best cards in the set. I vote A. A contextual point that I think they may have overlooked is that hitting 8 (enabling gamebreaking lines of cast+use, or threatening to use twice in one turn) gets easier with Treasure and with Explore.
• Tilonalli's Skinshifter -- This one got an F from LSV and a D from Marshall. This one's pretty bad and I don't think any sort of deck wants this, but it's not a blank card in any deck and isn't strictly unplayable... pretty close to that, though. D-.
• Shadowed Caravel -- Given a Build-Around F, which might just be right for this one, but I think it cracks into the D-/D range with perhaps 4-5 Explore creatures, particularly the repeatable rare ones. Granted, we're still talking about a card that's probably still worse than a Queen's Bay Soldier, but Build-Around D- seems more technically correct. The best kind of correct.