Caymen are created by the Herathians (shapeshifting spider/human alias) on the Savage Coast according the canon works of Bruce Heard in Dragon Magazine. They did make their first appearance indeed in AC2 as Religon already explained.
Here is a "evolutionary" timescale for the Lizardkin.http://6inchnails.deviantart.com/art/Reptilian-Timescale-510362391
That way you can see when in Mystara time they came to existence.
Why and how, but especially when these critters came to the Malpheggi, Blight swamp, Mucks Broken Lands, I do not know.Caymen – Caymas (Troglodytes Servilus Minor)
(to calculate XP values see Rules Cyclopedia or inside AC2 cover)
These reptilian humanoids stand about a foot tall, with bodies sheathed in rough brown or green skin. Their black eyes boast infravision with a 90-foot range.
Caymen are intelligent and sociable, dwelling together in villages. They can speak the Common tongue, their own language and sometimes the languages of other creatures of the area.
The last creation of the Herathians was almost a success. Backing away from the gigantic and deadly Gatormen, Herathians produced the small Cay-men. They were bred to become slaves and builders, smart enough to understand construction plans, agile and quick enough to do the job well and without delay, and small enough to make them weaker than their guards and easy to control.
That plan almost worked, except that the Cay-men weren’t as bright as expected and were terribly pretentious in addition. Their pride would get in the way when a construction flaw needed correction, or when the Cay-men simply disagreed with the architects!
Endless bickering separated the Herathian architects from their Cay- man servants. In the long run, Cay-men deliberately allowed flaws to remain in the Herathian monuments, without alerting the architects. Exasperated by a rash of catastrophes, Herathians gave up on the Lizard kin experiments, and dumped the Cay-men north of the Bayou.
The building skills of the present-day Cay-men are rather outré. They were never bred to become architects, yet Cay-men still attempt to build things to prove they are better than the kin of Shazak and Ator.
Their lack of understanding of sound architecture and engineering has led the Cay-men to erect such dubious structures as the Great Citadel of Cay (see “The City of Tu'eth”). These constructions do get in the way of raiding Gatormen who don’t know any better, but they wouldn’t last long against the experienced military of Bellayne or Herath. But that’s beside the point. Cay-men are still very proud of their accomplishments.
Caymen soon spread over Mystara and are found in nearly every large swamp (Including; Malpheggi in Darokin, The Mucks in Broken Lands, both swamp and Moor in Karameikos, etc.) using the same techniques.
Their native language sounds like simple hisses and chitters to other creatures. Fortunately, Caymen also speak the local language. In addition, some may know the languages of subterranean creatures living nearby.
Many of the sounds used in Lizardkin expression are difficult to reproduce with a Human’s vocal cords. In general, names are very short, one or two syllables at most. Cay-men hiss, wheeze, sneeze, whistle, hum, purr, or use a weak, lispy voice when communicating with Humans. Body language is used in conjunction with spoken words. For example, all of the Squamous ones use slight movements of their tails as punctuation or signs of courtesy and respect. Greater movements of their tails express deeper emotions. Lizardman also use quick motions of their forked tongues when thinking or when suspicious of something.
None of these creatures have any special abilities (see “Miscellaneous”). Young Lizardkin (i.e., player characters when they are first rolled up) each start with a relatively low Intelligence score, as shown on the Intelligence table below. Don’t forget to reward good role-playing of truly “primitive” characters! Each time one of these PCs gains a level, an Intelligence check should be rolled on 1d20. If the check is failed, the PC gains a point of Intelligence, up to the racial limits given in the Intelligence table. In other words, PCs gain in Intelligence as they gain levels, but the gain becomes increasingly harder to achieve.
Charisma applies only between creatures of the same race; penalize Charisma –2 when dealing with Humanoids, and -5 when dealing with Demihumans or Humans. The natural -1 penalty to Gatorman’s Charisma reflects the difficulty Gatorman have in getting along with each other.
Caymen usually avoid conflict, except in self-defence or when protecting their villages, territory, or food sources. However, cay-men know that they are not suited to fighting: they prefer to make quick attacks and get to cover before the enemy can respond. When pressed, they use large (for them) bone daggers (which inflict 1d2 points of damage), small javelins called Boks (which inflict 1d6 points of damage), and special grenades manufactured by Cayman Wokani. Each weapon inflicts 1d6 points of damage.
In general, Caymen dislike frontal assaults. They prefer to surprise an opponent, make a few quick attacks, then flee.
All Caymen can move silently and hide in shadows with a 40% chance of success. They use these skills to evade combat, or to surprise foes with whom they must fight; those attacked by a concealed Cayman suffer a -2 penalty to surprise rolls. Caymas are incredibly tough for their size; this is a deliberate feature incorporated by their Herathian creators.
All Caymen instinctively know how to swim. Cay-men can stay underwater without discomfort up to three minutes, and then hold their breath as long as normal Humans. All Caymen can hide in swamp vegetation (50% chance, at least 10’ away from observer). Caymen all have infravision of 90’.
Preferred skills: Hunter, Swimming, Animal Training, direction sense, hiding, Fishing, Foraging.
Racial Tolerance; Orc -4, Gnoll -4, Bugbear -2, Ogre -4, Gnome -1, Elf -1, Fairies -2, Troll -5, Human/Dwarf -2, Giant -4, Kobold+1, Hogboblin-3.
Traits; Cautious +4, Peaceful -2, Trusting -2
Caymen build underground villages of tunnels and chambers 1 to 2 feet high. They protect these lairs with palisades of packed dirt and woven reeds. The walls have many entrances, all of them the equivalent of concealed doors. The Caymas are inordinately proud of these structures and refuse to see any flaws in the designs, no matter how blatant.
Each Cayman village includes 10d6 adults, and half that many non-combatant offspring. Immature Caymen reach adulthood in one year. Villages are led by a shaman, equivalent to a priest of 5th to 7th level. These shamans live longer than the average Cayman (60 years, as opposed to the normal 40-year life span), so their hides grow tough and improve their Armor Class to AC 6. With a shaman in a Cayman party, the creatures’ morale increases by 1 point.
Not only do the better warriors use bone weapons and tools, they wear bone and feather headdresses. The more elaborate the headdress, the greater the warrior – though these Caymen avoid wearing such adornments in battle, not wishing to alert the enemy to their superior abilities.
These lizard-kin get along well with gnomes and tolerate lizard men. However, due to the Cayman’s small size, evil subterranean races often take them as slaves. Caymas tolerate Shazak and are afraid of Gurrash. Caymas are not necessarily hostile but are very leery of the "big" races. Often, Caymas have been taken as slaves by larger, evil races.
The people of Cay copied the social structure of the other Demihuman kingdoms and established their own monarchy. Queen Ssa’a presently rules the nation. She has been behind the Cay-men expansion into the open lands north of the forests around Rleeh’z and Hwool. There, the Caymen have learned a very primitive way of raising herds of wild Aurochs. For this, they domesticated small Lizardlike striders that they harness to small war chariots. Cay-men trade some of their Auroch meat with the kin of Shazak. Unbeknownst to Herathians, Cay-men also trade a little of their red steel, from a mine that is located next to Hwezzah. They are still in the process of learning how to forge metal. Cay-man metal-working is quite primitive, but their Wokani are learning.
Kingdom of Cay (Savage Coast)
Capital: Tu'eth (pop.: 8,900 Cay-men); ruler: Queen Ssa’a IV “Silver Tail,” daughter of Queen Roha’a II; Tribal domain includes forested land north of the Bayou; patrons: Kutul, Cay.
The City of Tu’eth —excerpt from the scrolls of Raman Nabonidus:
“Seen from above, Tu’eth reminded me of Halfling burrows. The city was a succession of small hills with wooden doors and round windows. It was an average-sized town, with most of the paths winding inward, more or less toward a small mesa, about 50’ high, in the middle. “At the centre around the mesa stood the Great Citadel of Cay. It was an amazingly rickety assemblage of planks, tree trunks, bamboo, stones, ropes, leather, nets, and random portions of adobe walls with arrow slits, all of which contrived to form a 20’ palisade. Several towers of respectable height (but debatable stability) overlooked the palisade at rather unpredictable intervals. Rope bridges, catwalks, and flimsy-looking drawbridges hung just about everywhere, running from one level to another like some sort of mad, three-dimensional maze. Surely, if an enemy ever climbed up the palisade, it would not be able to get back down the other side, for it would be hopelessly lost. “This ‘monument’ of Cay-men military architecture stretched for miles around the mesa, up and down the hills and crags, using large trees and boulders as anchor points. A 15’ wide moat full of muck surrounded the extraordinary creation. At the centre of citadel, within the mesa, lay the queen’s burrows.”
Intelligent and sociable, Caymas of the Savage Coast live together in villages, herding aurochs (large, shaggy bison) and trading Auroch meat and cinnabryl with the Shazak. Aurochs are about 6 feet tall at the shoulder, so the Caymas have some interesting herding techniques. A cayma herder usually rides an Auroch, using sticks with metal hooks on the end to tug on the auroch's ears, thereby directing it. Caymas have also domesticated small lizards (2 to 3 feet in length), which they use to pull their war chariots and as beasts of burden.
In the Mucks in the Broken Lands, they live similar, but instead use goats and shaggy sheep instead Aurochs. Here they train crocodiles and alligators instead of Lizards.
Shamans & Wokani:
Should the character decide to become a Spellcaster, he needs more experience points per level to achieve a higher character and thus casting level. The indicated XP have to be gained before actually acquiring the corresponding spellcasting level. This means that one can’t start with a spell-casting character when the PC is created. For example, if a 3rd level Cay-man wanted to become a 1st level spell-caster upon reaching his next level, he would need to reach a total of 16,000 XP instead of 15,000. In order to cast spells, a Shaman must have a Wisdom of 9 or better. A Wokani needs an Intelligence of 9 or better. All spell-casters must be at least 1st level in their race to be able to cast spells.
Cay— (alias Terra), Cay-men’s patroness: Cay represents earth, but also life, fertility, and good luck. Cay is one of the Immortals whom the Herathian experiments on Humans and other beings angered. She felt that creating a new race was truly admirable, but debilitating already existing ones in the process was odious. She caused the Cay-men to become useless to the Herathians by making them too proud and limiting their building skills (see the Codex of the Immortals, in the Wrath of the Immortals boxed set).
Kutul— (alias Kurtulmak), Cay-men’s patron: The Shining One was a late comer to the scene. He saw in the Cay-men an opportunity for increasing the number of his followers. At that time, the Cay-men were poor Warriors at best. Kutul contrived to have them create a caste of Warriors headed by Shamans devoted to him. Kutul now shares the leadership of the Cay-men with Cay, she taking care of the growth of their population, and he acting as the patron of war, fire, and territorial gains. He also balances Cay’s annoying lawfulness with his own brand of chaos.
Caymen enjoy eating giant-sized reptiles and amphibians but sometimes fall prey themselves to large predators. They make reliable guides in swamps.
Caymen and Kobolds, if they would ever meet, would be able to form a true alliance, which could be dangerous to other creatures around.
Caymas are just beginning to develop more complex lifestyles, and they have even begun to develop a simple monarchy. Caymas enjoy eating giant-sized reptiles and amphibians but sometimes fall prey to large predators. They make extremely reliable guides in swamps.
They are partially immune to fire (lowered by 50% damage + full Armor Value) and heat (they are in effect blessed and have a +2 on inititative and 25% on speed, and suffer 75% less heat damage).
In winter, or other Cold environment, Lizardkin become lethargic and slow (they need the sun to warm up. .In effect they suffer a condition equal to both a Blight spell and a Slow spell.
Important D&D DM Note;
Mystara D&D kobolds are different in appearance and origin when compared to other game systems and D&D worlds. On Mystara kobolds are a doglike breed of humanoid, and NOT, I repeat, NOT lizard-like, they aren’t even reptilian, NOT Dragon –related. The breed like any mammal, are not oviparous, have NO scales (except hairy scales on their tales). Kobolds are often depicted as being Lizard kin in recent newer editions of D&D art, but this is a mistake on Mystara. The "kobold" depicted lizard-like creatures in D&D3rd, 4th, 5th, etc are at best basic D&D Mystara Caymen, which would also declare their draconic link which is often given for kobolds in newer D&D editions, who were created canonically from Chameleonmen (partially draconic creatures).