Lion, Lizard, Lizard Man, Locathah, Lurker Above

AD&D Lions
While everyone is familiar with cats and claw/claw/bite routines by now, a lesser known feature of lions might be their bonus hind leg rake for an additional two attacks at 1d6+1 which occurs if both main paws hit. Basically, if you don't have good AC, fighting lions in melee will shred you.
Presumably because of their manes, male lions have +1 AC from frontal attacks.

The statblock includes mountain lions and spotted lions, which are smaller cougars and and larger Pleistocene cave lions, respectively.

AD&D Lizards
A bizarre entry far more fantastical than one might assume.

Fire Lizards are also called 'false dragons' and indeed are like a weaker sort of red dragon, with 10HD< AC as plate, a claw claw bite routine of 1d8/1d8/2d8, and an unimpressive small flame puff for 2d6 save for half. They themselves are immune to fire attacks. They sleep for long periods, hunt once a week from their subterranean lairs, and like shiny things.

Though not possessing the great hoard of a dragon, they do have treasure tybe B, Qx10 for many gems, and a 10% chance of having 1d4 eggs worth 5000 gold each. Unlike dragons, they are only animals.

One might assume this is a sort of 'fakeout' monster, where peasants are harassed by a 'dragon' and the party finds these things instead. They have a sort of appeal as alternate guard beast or mount that's dragon-like but not all too troublesome, but I can't imagine they are anyone's favorite monster.

Giant Lizards, ironically, are the smallest lizard in the lizard entry. While 15' long, they only have 3HD and a single 1d8 bite (2d8 on a nat 20 due to getting a good bite in) so they're kinda a 'whatever' monster.

Minotaur lizards are huge 8HD, 40' long beasts that deal massive damage(2d6/2d6/3d6 claw/claw/bite) and, on nat 20s, can hold people in their mouths- not a swallow hole, but a similar sort of auto-grapple. They are slow, but good at ambushing, and are usually found in their lairs with a scattering of loot from their victims. I don't know why they're called Minotaur lizards... maybe because they lurk in a lair as the minotaur did? Later editions give them horns, which makes sense, but no mention of horns is made in the AD&D entry. With numbers appearing of 1d8 they mostly seem like just a big beefy threat for deep dungeons

Subterranean Lizards seem to be some form of giant gecko, as they can run on ceilings and walls. Apart from the double damage nat 20 lizard bite, they aren't very interesting, but at least they could potentially get up to shenanigans in certain dungeon layouts compared to the Giant Lizard.

AD&D Lizard Man
A fairly uninspired entry about 2HD humanoids whose main claim to fame is being slowish on land but fastish in water, and having a claw-claw-bite routine with 1d2 claws. Also having pretty good art.

The entry mostly just goes on and on about how 'primitive' 'crude' 'tribal' etc they are and says some 'evolved' to a 'higher state' of using huts, shields, throwing weapons, and clubs, the better to eat people with. Gygaxian baloney instead of any actual lore, basically.

While I'm sure people have done better with lizard-men since then, the default entry might as well just be giant lizards.

AD&D Locathah
Ah yes, another 'underwater fishperson.' They ride giant eels and are 'nomads' who also live in a castle that has a 50% chance of a portuguese man-o-war trap, and have provisions for leader types who have no difference save for increasing HP.

I had forgotten these creatures existed, compared to Kuo-Toa and Sahuagin, and expect will forget them again soon enough after this post.

AD&D Lurker Above
Now THIS is a monster. "What if the ceiling was actually a giant manta ray monster that fell on you and smothered you to death."
They are very tough and non-intelligent, not even animal intelligence, fighting to the death against whatever they drop down upon. With mediocre AC but a fat 10HD, and a 1d4+1 round time limit before those trapped beneath are 'smothered.' An entire party can probably chop one up in time barring bad luck or all the fighters being trapped beneath with weapons too awkward to shank it with in hand (honestly with the number of such monsters in D&D, there is probably something to be said for walking around with an offhand dagger instead of a shield.)

Some interesting things are the good odds lurkers have fat stacks of gold coins as treasure, perhaps as incidental bait in the rooms they overlook. They also have neutral buoyancy thanks to a produced gas in their bodies, allowing them to fly despite being more like a manta ray than a bird.

All in all, a classic 'check the roof' monster of the upper levels, once the players have grown weary of green slime and piercers.

Sunset Realm Lions

Sunset Realm Lizards

So in the age of the 2nd sun, Yg-A, the world was very hot, the ice of the moonlands being driven far back by fiery dragons. It was a good time to be a reptile.

However, Yg, the cast-off skin of Yg-A the dragon sun, had other ideas beyond sitting in the sun and licking your eyeballs. Those reptiles who traded their legs to the snake-goddess Yg were granted wisdom in return, and so arose the Serpent Empire. The Reptile Kings, Frogs, Eels, etc all resisted, but were eventually subjugated by the big brained schemes of the serpents, adopting serpent tech but always being one step behind.. Lizardfolk were, according to ancient murals, equally comfortable on all fours or bipedal, with different tail positions for balance, and favored strength and rigidity, as a conscious opposition to the subtlety and flexibility of the snakes. Though the Serpents conquered them for the sin of 'keeping their legs' the reptiles were not wiped out by the serpents, but by the intersolar period after Yg-A became trapped in the earth. Free of the Serpent Empire the Reptile Rebellion's splinter-kingdom of fire and magma kept the ice and darkness at bay for a while. But by the time the Elves, Ningen, and Svart created the 3rd sun, it was too late for the lizard-folk. If, by chance, their fires continue to burn to keep the lizards warm anywhere, it is in the Beyond, a thawed circle of waning fire in a lightless expanse of gnashing glaciers beyond the reach of the daylit world. Even their ruins are rare to find in the current solar eras- there is one on the Fault, from which a resurrected mummified Reptile King failed to reach the Orb before Townlocke did, but most have been swallowed by the dark of the moonlands. Sometimes one might find 'lizard people' but they are the product of mad alchemy or divine miracles, not descendants of the forgotten rebels of ages past.

Locathah- Nah

now get outta my encounter tables you black-lagoon lookin discount sahuagin

Lurker Above- Simply, these are a type of giant wilderness killer mimic adapted more to caves, gobbling sabre-toothed tigers, hibernating cave bears and so on. Trappers, the floor version, are not a different species, but simply lying on the floor, perhaps after dropping from the ceiling to eat something earlier. Choice of ceiling or floor may be these creature's gender expression, and it is theorized that a Lurker and a Trapper will mate with each other when attempting to eat the same adventurer, who will presumably be smothered by the undulating Trapper/Lurker sandwich and used to feed offspring afterwards.

As mimics, they can change their texture and patterning to match ceilings or floors, but are more specialized than smaller mimics and become less and less convincing as the terrain becomes more advanced than a cavern. As such, while they could potentially infest a stone castle, certainly mines and dungeons, perhaps even external cobbled/brick roads, wooden domiciles are typically safe from Lurker/Trappers.

Unlike mimics, Lurker/Trappers are not intelligent enough to train, but they can be lured to key locations and kept there with a high rate of success if fed consistently and so used as guardians. They may wander in order to seek mates, however, so this tactic is used only by mad dungeon wizards rather than respectable members of society.