Is that anything? Does it even make sense. It's a prismatic golem. It has no physical form and is made from light gathered from the plane of Elysium. It has no Intelligence score and a neutral good alignment. What? It doesn't make sense? Fuck it, it's in the book anyway.
This book isn't quite as wild a ride as Planescape Monstrous Compendium: Volume III, but that's probably because it has Eberron to lean on. It's WotC's bold new campaign setting with soon-to-be-staple creatures like changelings and the warforged, so some of the entries, at least, are grounded in a firm campaign logic. But other times, it definitely feels like it's throwing stuff against the wall to see what sticks.
And some of it does, indeed, stick. That's when the book is at its best. Maybe I think the Hangman Golem should have been an undead creature made from used nooses stolen from the gallows, instead of what is essentially just a weird construct made from animated rope, but that's almost certainly what everyone thought when they first saw that creature, and it's such a memorable and interesting idea that it's practically an inevitable revision if this thing ever shows up in canon again.
Turning away from the "G" section, I could easily name another half-dozen creatures from this book that inspired and delighted me . . . so I will. The Armand, armadillo folk from the desert that specialize in martial arts. Dread Blossom Swarm, pretty flowers with spikes for roots. They are inexplicably from the Upper Planes and they will kill you. Plague Brush, a colossal tumbleweed. Crystaline Trolls. Topiary Guardians - trim your hedges into the shape of a triceratops, animate that triceratops with magic, and have it maul intruders. Forestkith Goblins. They change into trees during the day, and it's enough to remind you that in a better universe, goblins could have been Fey.
There's more, but I'll stop there. There are also some duds, of course, where it just seemed like they tossed a nonsense name on a perfunctory concept and called it a day, but my goodwill towards this book is pretty high at the moment, so I'm not going to call any of them out.
Overall, this book had a better balance of lore and mechanics, with many of the entries actually getting into some interesting worldbuilding. Despite the Eberron provenance of many of these creatures, the "X in Eberron" sections often felt like an afterthought, though. They're on roughly half the entries and I suspect the deciding factor of which monsters get them is nothing more or less than the remaining space on the page (the "X in Faerun" sections are even more blatant about this). When they were good, I was glad they were there, but "Cheliceras prowl the Howling Peaks, north of Zilrago" means less than nothing to me (it's been a while since I read the Eberron book). I guess it's a mountain range where this mountain-dwelling creature might live?
While we're on the subject of mechanics, I did make a conscious effort to be more mindful of stat-blocks this time around. . . but I don't think it did me any good, because I have no remaining 3.5 mechanical intuition. The Chelicera and Chraal are both CR 6 monsters, but the first has 19 AC, a BAB of +9, and 66 hp, whereas the second has a 21 AC, a BAB of +6, and 85 hp? I guess that's within the same ballpark, but I kind of feel like the Chraal is going to be a much more tedious fight.
That's just 3.5, though. The system was okay with characters of the same level having wildly different combat stats, so challenge rating was always going to be something of a guess.
Final thought - I really wish MMIV and MMV weren't so expensive on the secondary market, because this book feels like a real turning point. It isn't exactly where I want it to be, in order to be an ideal monster book, but it's probably the best one I've read for D&D since Planescape Monstrous Compendium Volume II.
Ukss Contribution: There's a magical war machine called a Slaughterstone Eviscerator, which the book implausibly claims is made of a single block of carved stone, despite the art clearly depicting a machine made of multiple metal parts (and also, the general silliness of making something that's intended to move out of a single block of stone). But despite my love for on-the-nose names that don't even pretend towards euphemism, it's not quite the machine by itself which drew my attention. Rather, it's the Eberron section, where it's put forward that these things, which, I remind you, are called Slaughterstone Eviscerators are used as protection in banks. Like, right in the lobby and everything. "Oh, hey, I'm new here, how do I find the teller?" "No problem, sir, it's straight ahead of you, just circle around the death machine with the giant blades and you'll see it."
What's that? We're going to have capitalism in our fantasy setting and one of the themes will be the relationship between private property and the ability of the bourgeoise to mobilize the violence of the state on its behalf? Fuck it, subtext is for cowards.