Werejaguar
Werejaguars, as the name suggests, are a species of werecat with the ability to turn into jaguars, the only American species of the genus Panthera. They're basically South/Central American werewolves, what more do you want?
D&D Werejaguars
The werejaguar was surprisingly popular in the days of Advanced Dungeons & Dragons, with three different takes on the monster appearing in three different settings; Mystara, Ravenloft, and the "universal" setting. After that, however, its popularity sharply waned; aside from the Dungeons & Dragons 3rd edition update of the Ravenloftian werejaguar, it hasn't been seen since.
"Generic"
The "generic" D&D werejaguar debuted in the Monstrous Compendium Annual Volume One; supposedly, it was based on the earlier Ravenloftian werejaguar, but there are sharp differences between the two - most notedly, this breed of werejaguars is notedly malevolent, which is not the case with their counterparts from the Demiplane of Dread.
The generic werejaguar is a human or demihuman capable of assuming three forms; its humanoid form (which may have sandy blonde hair streaked with black, or vice-versa); a large jaguar perhaps 7 feet long from nose to rump; and an anthropomorphic hybrid animal form: broad snout, blackmarked sandy pelt, wide paws that retain opposable thumbs, and a long, expressive tail. These werejaguars fear only the touch of enchanted blades or weapons made from obsidian, and are fatally susceptible to mercury poisoning.
These werejaguars have a distinct prefernece for life in the wilderness, where they live either alone or in temporary family groups consisting of a mated pair rearing their one or two cubs; like the animals they resemble, werejaguars don't marry, though they do tend to have preferred mates that they will usually go for first. Females tend to only mate with other werejaguars, but males are far less picky, often seducing as many humanoid women of compatible nature as they can and then hightailing it out of there before the women learn they've fallen pregnant with monstrous offspring. That said, some werejaguars enjoy living in villages or small towns, but they are commonly uncomfortable in larger settlements (towns with a population of over 100, for example). Bearing this loose limitation in mind, they frequently prove very adept at infiltrating human society. In town, werejaguars can easily set aside their solitary tendencies and cooperate with others for as long as necessary. However, a werejaguar who has infiltrated human society will increasingly yearn to seek out an isolated area in which to relax and be alone.
Like many werebeasts with an actively predatory alternate form, werejaguars are pure carnivores, and they subsist only on freshly killed meat. Though they can subsist on animal flesh just fine, generic werejaguars prefer the flesh of sapient creatures - a marked difference to their Ravenloftian counterparts.
Ravenloftian
The werejaguars of the Demiplane of Dread are very different to their counterparts on other words. They appeared in Van Richten's Guide to Werebeasts for Advanced Dungeons & Dragons, and were then converted to Dungeons & Dragons 3rd Edition in the Denizens of Darkness (3.0)/Dread (3.5) splatbooks.
Werejaguars are lurking in the darkest hearts of jungles, usually living in and around old ruins long ago forgotten by locals. They venture from their secluded homes only to hunt and patrol their wilderness territories.
Werejaguars have but a single form, that of a hybrid humanoid/jaguar. This allows the creature to walk upright like a man or on all fours for running. Their pelts are spotted like their namesake and fur covers all areas but the face and palms. Their clothing tends to be strange to most of Ravenloft’s denizens, featuring brightly covered loincloths and wraps that cover a single shoulder and the chest area. Werejaguars often use tools of obsidian, but prefer their teeth and claws in combat.
In addition to the common tongue of men in their area, werejaguars speak a growling, hissing language of their own.
Combat: Werejaguars are silent, deadly hunters. They move through even the thickest of brush with hardly a sound and strike without warning. Because of their natural hunting prowess, anyone attacked by a werejaguar in a jungle or similar setting suffers a -3 penalty on his surprise check. Further, the creature’s own keen senses of smell, hearing, and eyesight make it impossible to surprise without magical aid of some sort.
The fearsome claws of these deadly beasts are employed in a pair of slashing attacks that inflict 1d4 points of damage each. In addition, the creature can bite its enemies for 1d6 points of damage. Because they are not true cats, werejaguars have no raking attack.
As with other lycanthropes, werejaguars are immune to weapons of less than +1 enchantment. They are unafraid of silver, however, for their bane is the hard wood of the ebony tree. Weapons fashioned from this material are able to strike the creature even if they are not enchanted in any way.
Werejaguars are unusually vulnerable to fire, suffering 1 extra point of damage per die of any such attack. As such, they greatly fear flames used against them in combat. Werejaguars confronted with torches or similar flames must make a successful saving throw vs. paralysis to attack. Larger flames or multiple sources force the creatures to save with a -4 penalty. Failure prevents the creature from coming within 10 feet of the fire. If a werejaguar suffers damage from flames, it must make an immediate Morale Check with a -4 penalty or flee for 5-20 (5d4) rounds.
Habitat/Society: Werejaguars form tightly knit communities carefully hidden from the eyes of humanity. They do not normally hunt intelligent creatures, even those of an evil nature, but will kill those who threaten their pack without mercy.
When outsiders enter their lands, werejaguars will often hunt them for sport. A victim will be toyed with, catching only fleeting glimpses of the lightning quick cats as they dart to and fro in the jungle. This torment can continue for hours or days, depending upon how fearful the prey is. Only when the cats tire of their fun will they move in for the kill. When that happens, they strike quickly and without mercy.
Werejaguar groups of 10 or more always have a 6-Hit-Die leader. There is a 20% chance that the leader is lawful evil. If that is the case, the pack will tend to roam far outside of its territory, hunting down all sentient species it comes across.
Ecology: Werejaguars live on a diet of meat, usually taken from the dense jungles in which they live. In truth, many of the lycanthropes dislike the taste of sentient flesh. They say these creatures taste bitter and unhealthy.
As territorial as they are, werejaguars serve as the custodians of their jungle homes. Much as a druid or ranger character might oversee an expanse of forest of wilderness, they strike quickly against any force that might upset the balance of nature around them.
Mystaran
The Mystaran werejaguar first debuted as a PC race-class in PC4: Night Howlers for BECMI, whilst it was then converted to a monster for Advanced Dungeons & Dragons 2nd edition in the Mystara Monstrous Compendium Appendix.
This later version of the Mystaran werejaguar is portrayed as a savage monster, even worse than the generic D&D werejaguar (Chaotic Evil to its Neutral Evil).
Mystarans know werejaguars as the scourge of tropical rain forests: solitary, extremely effective hunters. The werejaguar has three forms: completely human, a human-jaguar hybrid, and a jaguar with glowing red eyes.
In their human form, werejaguars are generally lithe, athletic folks, with long limbs and very sharp hearing. Their mood varies between quiet but alert contemplation of their surroundings to a harsh, controlled, predatory rage. In this form, werejaguars act impatient and short-tempered in cities.
In their hybrid form, werejaguars boast elongated and very muscular legs. Their torsos remain human, but also grow much more muscular. Hybrid forearms end not in human hands, but in prehensile claws. The feet feature claws, too (not shown here), enabling the creature to rake an enemy. In this catlike humanoid form, a werejaguar can walk upright or run on all fours. The hybrid has a jaguar’s head — one still capable of human speech and facial expressions.
The pure jaguar form cannot speak, but does retain human mental faculties, plus the animal’s bunting instincts. Only the glowing eyes indicate its lycanthropic nature.
Combat: Werejaguars do not simply rush headlong into attacks. Rather, these hunters stalk their prey in the wilderness and choose a moment of weakness to attack.
In their jaguar state, these lycantbropes can climb quite well; they scale trees and cliffs as thieves climb walls, with a 95% success rate. Because of their feline stealth and natural camouflage in rain forests, opponents suffer a -2 penalty to their surprise roll. A werejaguar also gains a +1 bonus on its initial attack roll when leaping from above onto prey.
In combat, the werejaguar can rake a victim with its two rear claws automatically for 1d6 hit points of damage if both front claws strike successfully that round. The creature can use this attack form in both its pure jaguar and hybrid states.
The creature can summon 1d2 normal jaguars that will arrive in 1d4 rounds. In some cases (25% likelihood), 1d4 jaguars will be with a lycanthrope when a party encounters it. Like other werebeasts, werejaguars are hurt only by silver weapons.
Habitat/Society: Werejaguars have no interest in seeking out or working with their own kind. Each has its territory and almost always meets a fellow werejaguar in trouble with indifference.
True werejaguars (born to lycanthropy, not infected with it) myte only once. After producing a litter (1d8 kittens), the two split up again. The female spends a year caring for the young.
Contrary to popular lore, true werebeasts change form at will; unaffected by phases of the moon. Only infected lycanthropes unwillingly change shape during the full moon. True werejaguars cannot be “cured” of lycanthropy.
Some rain forest tribes fear werejaguars, revering them as minions of evil Immortals. Rumors tell of savage werejaguars able to cast clerical spells; these cats, witch doctors in hidden villagesm devour victims in service to their Immortals.
Ecology: Werejaguars hate weretigers with a passion, loath to share hunting ground with another feline lycanthrope. In the twilight, they enjoy hunting game, from animals to humans.
Werejaguar PC Race-Class
Werejaguars are amongst the myriad therianthropes who received a writeup as a BECMI race-class in PC4: Night Howlers.