Mind Flayer – Like the Hags, the Mind Flayers show up in lots of other entries. They are the big bad behind a lot of terrible things, and while there’s only one stat block (one and a half, really) it’s a solid CR 7 enemy with some handy tricks – magic resistance, mind blast and, of course, brain eating. The lore is flavorful enough in its own right, but it’s really just part of the larger tapestry woven throughout the book. All in all, quite satisfying.
Minotaur – Another CR 3 brute, and at first glance it seems pretty straightforward with charge and berserker attacks, but the lore takes an entertaining turn when talking about the origins of minotaurs in mystery cults (which in turn provide a potential source for labyrinths) which offers some fantastic opportunities for minotaurs as plot drivers and as random brutes.
Modrons – I know some people might go “huh”, but for a planescape fan, this entry inspires a happy little dance, as evinced by my dancing which you quite thankfully cannot see. I am utterly incapable of viewing this entry in any kind of real critical fashion because its presence delights me so, right down to it’s art, which is not quite Diterlizzi, but clearly bears the marks of inspiration. We get statblocks for the first five modrons (monodrone, duodrone, tridrone, quadrone, pentadrone) ranging from CR 1/8 to CR 2 (Though the pentadrone seems a rather nasty CR 2, with 5 attacks and paralyzing gas) and enough color and lore to give guidance for how to play them and strongly implies the rest of their structure, right up to Primus.
Mummies – There’s some nice material regarding the source of mummies, with the important note that there is always a creator (because mummy status is explicitly a curse) and often some manner of trigger that causes it to rise. Like so many of the better monsters, the mummy has a built in story that makes it a plot waiting to happen much more than a creature sitting in a room waiting to fight.
The baseline mummy is CR3 with a fear-inspiring gaze attack and a rotting touch. Mechanically, if you blow the save, you reduce your HP maximum by 3d6 every 24 hours, and you can’t heal. Super nasty, and a good reason to have remove curse on hand. This is the mummy you’re going to find in a generic adventure encounter.
The Mummy Lord is closer to something from a horror movie. CR 15, with legendary and lair actions as well as regional effects which include a curse on anyone taking something from the mummy’s tomb. It’s easy to see this as the villain for an entire campaign region.
Myconid – I’m pretty sure there are people who feel about myconids (mushroom men) the same way I feel about modrons, so I wish them well of it. They’re a nice addition to the underdark (along with the flumphs, offering some good guys) full of mental communion and hallucination-filled dreams. They’re also pretty creepy, since their minions basically include pseudo-zombies animated by fungal spores.
Naga It’s almost a throwaway line, but the origin story of the naga (servants of an ancient race who view themselves as the natural heirs). The good (Guardian) and evil (Spirit) naga are magically potent (CR 10 and 8 respectively). They’re also pretty much immortal, coming back after a few days from anything short of a wish.
This tidbit is what makes the Bone Naga (undead naga, CR 4) more interesting. Basically, the Yuan Ti got sick of the Naga constantly coming back, and so came up with a ritual to break the cycle, creating undead Naga. All in all, these guys make for fun, smart opposition.
Nightmare – Another mount, not hugely interesting, since Nightmares are usually just adjuncts to the real bad guy. That said, the color surrounding their creation (the torture and sacrifice of a pegasus) is nicely vivid.
Nothic – I guess these guys came from the miniatures game, as I admit I did not recognize them when they showed up in Phandelver. That said, the lore for these guys is fun – Vecna effectively left traps on his own ascent to godhood, and wizards who follow in his path occasionally encounter them and are reduced to these monstrosities. They still pursue arcane knowledge, albeit in a twisted, semi-incoherent way. It’s a good story, and it gives a nice justification for these things to show up in interesting places.
Ogres – Ah, the classics. At CR 2, these guys are just brutes, but that’s exactly what they’re supposed to be. Nothing too exciting in their lore, but they don’t really need it. The entry also includes Half-Ogres (Ogrillion) which, I admit, serve rather less purpose. “Like ogres, but less so” is not much of a pitch. In other fiction, they’re a bit more interesting, emphasizing that they’re smarter opposition, but there’s none of this in the entry.
Oni – AKA Ogre Magi, these guys have always been nasties, and all of that translates appropriately into this stat block – shapeshifting, regeneration, gaseous form, cone of cold. The lore is flavorful, but mostly just feed into the means of playing these guys (which is to say, emphasizing that they’re pretty terrifying)
Oozes – Black pudding, gelatinous cubes, gray ooze and ochre jelly all fall under this entry. Black pudding are still the nastiest, but functionally they are quite similar in their play (climbing walls, attacking with pseudopods) with some specific things like weapon destruction. Gelatinous cubes play a little bit differently, as they still focus on moving and engulfing, but that is also well supported (though I admit, it feels like the cube was really the perfectly expressed 4e monster.)
Orcs – When we talk about classic humanoid monsters, the orc is pretty much the baseline, and this entry is decently in line with that. It draws a broad enough picture to give orcs a little social context and a mythos which pits them against the other races (and also justifies halfbreeds). Stat blocks are given for a classic orc, an orc warchief, an Eye of Gruumsh (blessed by the chief god of the ord) and the Orog, who is sort of an orc-plus (CR 2).
The Orog may seem like a weird addition, but it’ll be familiar to fans of Birthright – the Orogs were the orc replacement in that setting. Explicitly, Birthright humanoids were very clearly nations, and the Orog ranged in power, allowing them to fill gaps that would otherwise be filled by a wider range of humanoid races. The net result felt a lot more coherent, and the presence of the Orog makes it a little more possible to spin the Orc entry in that direction.
Otyugh – This entry is a lot more boring than I expected. Tentacles, telepathy, general badness, that seems like the it should be really unpleasant, but it just comes across as kind of meh.
Owlbear – The owlbear suffers unfairly from comparison to the 13th Age owlbear, who explicitly includes rules for ripping off arms and running off to eat them. Not that this owlbear is bad – it’s just a tough comparison. And it makes a decent effort – the lore is fun. especially regarding the challenges in training owlbears. The reference to rural communities having owlbear races is utterly delightful.