Pegasus – Oh boy, a mount. Excepting the fact that Pegasi are explicitly celestial in nature, this seems pretty bland.

Peryton – This is one of those crazy creatures out of folklore whose schtick (sometimes it has the shadow of a man) is creepier in the telling than in the actual encounter. The lore entry nicely updates the mythology and gives a bit of monstrous motivation, but it’s ultimately more interesting from a tactical perspective, as the statblock is full of aerial effects.

Piercer – These dudes are ugly. And they’re a classic gimmick monster, dropping from the ceiling on unexpecting foes. They’re pretty much one-and-done, since when they miss, they don’t have much else they can do. Its presence is a little weird, since I thought the darkmantle had effectively replaced them in the dungeon ecology, but I guess you can’t have too much death from above.

Pixie – Basically, tinkerbell. Fragile and small, they have enough magical power to be dangerous opponents – anything that can fly and stay invisible is a real hassle. As written, they’re more designed to be an active annoyance (something compounded by the fact that they don’t speak common) and some GMs will love this, others will probably just shrug and move along.

Pseudodragon – This entry is basically the familiar pipe dream. Telepathy, magic resistance (which confers to its partner) and a poisonous sting. Which is fine, but there it is.

Purple Worm – Another classic – Shai-halud of the underdark. They’re huge and tough, and can swallow folks whole, all while carving out new caverns and generally keeping the ecosystem moving.

Quaggoth – Basically these are the yeti of the underdark. Big, animal-ish humanoids and sometime brute squad for the drow, with the occasional psionic member of the tribe. They have some interesting history and ancient enmity with the elves which is at the root of their history (drove them underground, allied them with the Drow).

Rakshasa – Functionally, they have a lot in common with the Oni – smart, magically capable, shapeshifters and illusionists but generally tough. Specifically, the rakshasa, have more of an extraplanar vibe to them, compounded by the fact that when they die, they just come back in the 9 hells, albeit weeks or months later (at which point, a plane shift gets them back).
In 1e, the way to kill one of these was with a blessed crossbow bolt, and they were basically immune to all other non-magical damage. They’ve kept the immunity, but they found a new and interesting way to represent the weakness.

Remorhazes – Another largely tactical monster. The young ones (CR 5) and the adults (CR 11) are structured similarly (burrowing and dangerous heat) though the older ones are also capable of swallowing.

Revenant – A plot monster – the actual revenant itself is just a fairly tough undead who will NEVER STOP COMING. You may encounter one as part of another plot, where you may be helping it or trying to figure out how to stop it, which makes it pretty useful in a number of ways.

Roc – Nice backstory – the Rocs were created by the gods of the giants to give an airborne weapon against giants. They’ve gone their own way since then, but that tie gives things a nice bit of flavor. Beyond that, they’re flying brutes – lots of HP, lots of damage.

Roper – I actually really dig that they decided that these guys are what piercers grow up to be. Beyond that, they’re mostly gross and tactically fun – the tentacles and giant mouth make it easy to see how the fight would go.

Rust Monster – The true terror of the dungeon! Hit points? Health? Disease? None of those are nearly as frightening as losing gear. The mechanic is actually similar to what we saw with some oozes (weapon takes –1 when it hits, when it goes to –5 it’s destroyed) but this incarnation is actually much kinder than some in the past, as it only effects nonmagical gear. This is probably appropriate, since it’s a little more apt to have it be a low-level menace than the kind of thing that makes 20th level fighters cower (and, yes, flashing back to the cartoon in the 1e DMG).

Sahuagin – These are the real bad guys of the sea, which is what makes the Merrows seem a bit redundant (though I suppose they’re ogre-equivalent). Evil shark people are always a welcome addition to the mix, and their bits of lore (like their worship of the shark god) and the occaisional mutant who can pass as an aquatic elf.

Really, the only weird thing about this entry is that it hinges on the war between the Sahuagin and the Aquatic Elves as a big setting element, and this is the first time we’ve heard any mention of aquatic elves (and no mention of merfolk and merrow). It’s a bit of a shame. A lot of the monster entries have a story woven behind them that makes for a bigger sense of the world. The Sahuagin hint at that, but it feels like the pieces aren’t all in place.

Salamanders – Like the galeb duhr and the invisible stalker, this is one of the more colored elemental. And speaking of tying things together, the salamander’s origin ties back to the story of the Azer and the City of Brass. They come int two form – CR 1 first snakes, and CR 5 full salamanders, with humanoid torsos atop the trunk of a snake.

Satyr – This is a curious one – the actual satyr has little in the way of magic on its own. It is only in a sidebar that the Satyr’s pipes are mentioned, though they have all the magic that one might expect.

Scarecrow – Low level construct with horrific overtones. Honestly, the art conveys more than the text for this one. Practically, it’s a bit hard to use it’s ability to hide, motionless, except against NPCs. When the GM mentions that there’s a scarecrow, that kind of shows her hand.

Shadow – Fun, low level undead with a strength drain, I think my favorite part is that as they are created, the target’s shadow darkens and breaks free when it dies. Most delightfully, if the target is resurrected, the shadow is still running around out there, and knows that it’s “parent” is back. I admit, this kind of makes me totally willing to kill a PC with a shadow just t set up that dynamic.

Shambling Mound – This is a classic made much more interesting by its color text. It’s a huge, tough, slow moving “plant”, a danger which is easily avoided is you’re aware of it (and have room to run) but which has a profound impact on the local ecosystem.

Shield Guardian – Basically, this is canned muscle for a spellcaster – if you control the amulet, you control a CR7 brute with heavy armor, regeneration, a bit of magic and some protection capability.

Skeletons – lovely pluralized entry, with the baseline (CR 1/4), the big one (CR2) and the warhorse (CR 1/2). No real surprises, but a solidly useful entry.

Slaadi Another planescape favorite, there’s a wonderful bit of extra lore here, as the Spawning Stone of the Slaad was apparently created by Primus (lord of the Modrons) and cast into the chaos of Limbo, with the Slaadi as an (apparently) unexpected side effect of the process.

The slaad themselves are classics – Red, Blue, Green, Gray and Death. They’re all terrifying, though their challenge range is lower than I’d have expected (capping at 10 for the Death Slaad). And, of course, their ability to infect humanoids to create new Slaad creates an extra layer of creepy factor.

Specter – This one took an unexpected turn. Classically, specters are one of the nastiest forms of undead, just a step below vampires, largely because their energy drain (2 levels!) was so terrifying. This version is much less terrifying – it still has life drain (damage that reduces max HP rather than levels) but it’s a CR 1 creature that is more noteworthy for being a flying, incorporeal horror. In fact, there’s a whole sidebar on a poltergeist variant which is always invisible and adds telekinetic effects

For all that this is a step away from tradition, it feels like a good step. This is much more of a horror monster than the usual “grey guy with grabby hands” and it seems like it would be much more fun to run.

Sphinxes – 2 kinds of sphinxes (androsphinxes at CR 17 and Gynosphinxes at CR 11). Notably, none of them are “the one with boobs” for those flashing back to the MM 1. They’re basically created by gods, which gives them an interesting bit of extra backstory – they’re powerful enough to suggest a private relationship with that deity.

Their personal badassness is pronounced, but it’s their lair actions really shine. They allow the sphinx to mess with time, and shift conversations into wacky demiplanes, so the whole “move the talk onto a giant chessboard” is now mechanically supported.