Continuing with the 1e Monster Manual... some notes on monsters that became core for the first time in 1e, and their status today.
Core in every edition since 1e: beholder, bugbear, bulette, carrion crawler, displacer beast, doppelganger, ettin, gelatinous cube, flesh and stone golems, imp, lich, lizardfolk, mind flayer, otyugh, owlbear, pseudodragon, rakshasa, roper, giant poisonous snake ("deathrattle viper" in 4e), stirge, troglodyte, umber hulk, wererat, wolf, dire wolf.
Core in every edition since, except 2e: hezrou and vrock demons, ice devil (gelugon), night hag, succubus. All were presumably too "satanic" for the 2e core rules, but - like many other 1e demons and devils - did appear in 2e's planar monster books.
Core in every edition since, except 3e: Nothing!
Core in every edition since, except 4e:
- A lot of normal and giant animals: 4e seemed to favor magical versions of animals over normal ones, although this had softened a little by the time of Essentials. FWIW, Monster Manual 2 brought back giant centipedes and tigers, and Adventurer's Vault brought back camels and elephants. (Dogs, surprisingly, only returned in an issue of Dragon.)
- Metallic dragons: The only time after 1e these weren't core, held back for Monster Manual 2 and their dedicated Draconomicon book. (It's been suggested the designers were averse to good monsters in 4e, at least early on; this does add evidence to that.)
- Mimic: This didn't return to 4e until Monster Manual 3, alongside 1e's ghast, quasit, and shadow. And unlike some other late 4e additions, it didn't make it to the Monster Vault. Considering how common this monster is in fantasy video games, you'd think it would have been front and center. (It was beaten to print by the less iconic ankheg, couatl, phase spider, remorhaz, will o'wisp, winter wolf, and xorn, all in MM2.)
- Lamia: There was a 4e lamia, but it was radically different from the one in other editions, clearly a new creature. While interesting in its own right, that only makes me wonder why they didn't give it a new name.
- Clay golem: These and iron golems were left out of the 4e MM and appeared in MM2, but iron golems later made it into the Monster Vault. Considering clay golems are the closest to their legendary origins, it was odd to make them non-core twice.
- Ghost, storm giant, harpy, hell hound, homunculus ("clay scout"), guardian naga, nightmare, oni (ogre mage), sahuagin, salamander, satyr, shambling mound, (andro)sphinx, worg: These were core only in the 4e Monster Manual, but didn't make the cut for the Monster Vault.
- Rust monster: These weren't core in the 4e Monster Manual, but (like the iron golem) rejoined the core in the Monster Vault.
- Blink dog, dragon turtle, sea hag, spirit naga, violet fungus: Didn't appear in 4e at all.
Core in 1e and 5e, but no editions between:
- Axe beak, allosaurus, giant goat: For whatever reason these three became non-core obscurities after 1e, but made a core comeback in 5e. Monstrous Compendium Annual 2 (2e) had all three, however (along with other 1e monsters that had fallen by the wayside, like the rhino).
- Manes: The weakest of demons was relegated to non-core books in 2e, like many other 1e demons... but while most other demons became core again starting in 3e, the manes remained non-core until 5e. (The lemure, by contrast, did get to be core in 3e.)
Non-core in 5e:
- Archdevils and Demon Lords: Excepting 4e (where Orcus was in the MM), these had been pretty solidly relegated to non-core books after 1e, so not a surprise 5e treated them similar. (Though one wonders if we would have gotten the classic Archdevils at all, if not for James Ohlen's DM Guild products.)
- Volo's Guide to Monsters brought back the catoblepas, leucrotta, morkoth, rot grubs, slithering tracker, trapper, some dinosaurs, and a few other animals from 1e. Mordenkainen's Tome of Foes only reprinted the Demon Lords and one Archdevil from 1e (and the former were reprints). Clearly the former was aiming more at old-school representation...
- Larva: Buried in the DMG.
- Ixitxachitl: Reasonably prominent until 2e, these became less so after. They didn't even get ported from Out of the Abyss into MTOF, like other monsters from the book.
- Dragonne (liondrake): These had been core in 1e, 2e, and 3e, but disappeared in 4e and had stayed gone in 5e... until Fizban's.
- Spotted lion, giant lynx, giant ram, giant tick, titanothere: Glory of the Giants seemingly made a point of bringing back these forgotten 1e-2e giant animals.
- A handful of other lesser-known 1e core monsters were only updated in adventures: the ice toad (Tyranny of Dragons); the su-monster (Tomb of Annihilation); the giant crayfish, lacedon, and sea lion (Tales from the Yawning Portal); the amphisbaena, giant (sea) eel, koalinth, and locathah (Ghosts of Saltmarsh); and the neo-otyugh (Infernal Machine Rebuild).
Not in 5e:
- Like the Rules Cyclopedia, a lot of 1e monsters have yet to make a return for 5e (even as some recent products have tried to fix that). Also like with the RC, I'm going to be picky with the below highlights.
- Eye of the deep: One of the first beholder-kin, yet it hasn't returned since 3e. Not really sure why, since we've gotten other variant beholders in 5e (even the obscure astereater, as Spelljammer 5e's "eye monger").
- Nymph: Discussed a bit in the other thread, these were core until 3e and made a non-core appearance in 4e (MM3). The only nymphs we have in 5e are the Theros versions, very different from the D&D flavor. (The hippocampus is another that only exists in Theros form.)
- Triton: A staple through 3e, which disappeared in 4e. In 5e, of course, it only exists as a PC option.
- Lernaean hydra: This hydra's unique shtick was regeneration... but after the 3.0 Monster Manual it disappeared, with hydrae regenerating by default after. (Notable exception: the default hydra in the 4e Monster Manual.)
- Pyrohydra: This was in every edition except 5e (even 4e, as the "flamekiss" hydra). Not sure why the current designers would object...
- Criosphinx and hieracosphinx: Like the dragonne/liondrake, these were staples until 3e, then disappeared. I suppose by 4e the designers figured we just needed the two sphinxes? (The heroic lammasu and shedu followed the same trajectory, core until 3e then gone.)
- Aerial servant: Part of the elemental "air kin" in the 2e Monstrous Manual. Unlike its teammate, the sylph, it disappeared entirely after 2e. (Redundant with the invisible stalker?)
- Leprechaun: Hasn't appeared since 2e. Not really sure why, since they're still a thing in pop culture. EDIT: Actually, they apparently returned in 4e! But still not in 5e. Updated the spreadsheet, anyway.
- Brain mole, thought eater: These psionic monsters were already being excluded as soon as 2e, where they were cut from the original MC Vol. 1 and 2. However, they were restored for the Monstrous Manual. In 3e they were strictly in psionic books. In 4e the thought eater returned one last time (as a "fell taint") in MM2, while the brain mole was relegated to joke status in Fool's Grove.
- Floating eye, masher, wind walker: These oddballs were already non-core by 2e, and absent ever since (excepting the masher's single appearance in 3e Dungeon).
- Giant beetles: Including the fire beetle, these were staples until 2e. 3e cut them back to just bombardier, fire, and stag. From 4e onward it's just been fire.
- Hazards and diseases: A number of monsters stopped being monsters in later editions. This included the cerebral parasite (3e/4e disease), ear seeker (4e disease) and brown mold (3e/5e hazard).
- Lots of dinosaurs: I'm not actually that surprised that later editions didn't carry forward the legion of dinosaurs in the 1e Monster Manual. Even 2e had already relegated a lot of them to non-core MCs.
EDIT: Forgot to note 4e monsters that were only core in one of the two books.
