"I am the night."
- – Batman
If you go way back into mythology, werewolves and vampires were often connected. So, of course Dungeons & Dragons decided to exploit this by creating a creature with traits of both: enter the Werebat, a therianthrope with a taste for blood and the ability to become a giant bat!
Werebats originated in the Demiplane of Dread, because Ravenloft is crawling with so many vampires and therianthropes that it needed a creature that combined traits of the two. They originated in the adventure "The Baron's Eyrie" in Dungeon Magazine #58, before making their way into official stats in the Ravenloft Monstrous Compendium Appendix I, and from there to the Monstrous Manual in Advanced Dungeons & Dragons. They also got a werebat Darklord named Captain Monette in the splatbook simply titled "Darklords". Strangely, in Dungeons & Dragons 3rd Edition, in a spectacular display of an editing cock-up, though the Werebat's ability score adjustments and bonus feats would be listed in the Ravenloft Monster Manual equivalent, "Denizens of Darkness", the actual monster statblock would be completely missing! And even worse, they'd carry this same error over to "Denizens of Dread", the 3.5 updated version of the manual!
Dungeons & Dragons 3rd Edition also saw the reveal that werebats can be found in the Forgotten Realms, with the splatbook "Monsters of Faerun" providing stats for them. This would lead to the creature returning in Dungeons & Dragons 5th Edition in the adventure "Waterdeep: Dungeon of the Mad Mage.
Despite all this, werebats are not restricted to D&D. Pathfinder states that they are native to Golarion as well, with them debuting in the adventure "Broken Moon", part of the Carrion Crown Adventure Path. They wouldn't formally get written up until the Pathfinder Bestiary 4.
Like the other species of lycanthrope found in Ravenloft, two varieties of werebat exist — natural (or true) and infected. True werebats are those creatures who have been born to werebat parents. The parents may be either true or infected werebats themselves, but the offspring of any two werebats is a true werebat. In those rare cases when a child is born with one werebat and one human parent, there is a 50% chance that it will be a true werebat and a 25% chance that it will be an infected werebat.
True werebats have three forms: normal human, vampire bat, or hybrid. In the first form, it is marked by bat-like features and traits (an aversion to bright lights, keen night vision, a taste for blood or raw meat, etc.). In its vampire bat form, it looks just like a common vampire bat. By far the most feared of its forms, however, is that of the hybrid. In this form, it retains its humanoid shape but takes on the added features of a bat. The arms extend to become willowy and leather wings form under them, the teeth sharpen into deadly fangs, and the snout protrudes from the face. The nails stretch into deadly claws and the eyes spawn an inner glow when light hits them.
Infected werebats have only two of the three forms listed above. Most (75%) have a human and hybrid form, while the rest have only a human and true bat form.
Combat: The type of attacks employed by a werebat depend upon its form. In human form, it will depend upon weapons to inflict damage, for its bare hands inflict but 1d2 points per attack. If at all possible, the creature will avoid combat in this form.
In bat form, they attack just as if they were bats. Each round, they may attack once and inflict but a single point of damage with any successful strike. The bitten victim, of course, stands a chance of contracting lycanthropy (see below), even from this meager wound. Opponents of a werebat in this form will find that it is unusually resilient, for it has its full human-form hit points.
In hybrid form, the werebat does not have the manual dexterity to employ weapons effectively. However, its deadly sharp claws and needle-like teeth make it far from helpless. In each round it may strike twice with its claws (inflicting 1d4 points of damage each). If both of these attacks hits, it may follow with a vicious bite that does 2d4 points of damage. Werebats can fly in their hybrid form and often use this ability to their advantage in combat.
Anyone who takes damage from a werebat’s natural attacks stands a chance of contracting the disease of lycanthropy and becoming an infected werebat. Every point of damage done indicates a flat 2% chance per point that the victim will become infected. The procedures for curing an infected lycanthrope are given in Chapter 5 of the Ravenloft Boxed Set.
Werebats can be harmed only by silver or +1 or better magical weapons. Any wound inflicted by another type of weapon knits as quickly as it is inflicted, hinting at the creature’s true nature.
Habitat/Society: Werebats favor caves in lightly wooded, temperate regions as their homes. From here, they can fly out and seek prey from which they can draw the blood necessary to satisfy their thirst.
Werebat caves are commonly home to only one family of werebats (two parents and 1-4 young). The young remain in true bat form until they reach 3 years of age. A this time, they mature into adults and, within a single year, become fully grown. This time of transformation brings out a great hunger in the creature, which forces it to spend most of its time hunting and feeding. Human villages near a werebat cave will certainly lose many citizens to the feasting of the ravenous creature at this time.
In addition to the werebat family, each cave will contain 20-200 (20d10) common bats and 1-10 giant bats. All of these lesser are under the command of the adult werebats and will act as their sentinels and companions.
Ecology: Although werebats favor humans and demihumans as prey, they have been known to feed on the blood of other mammals (like cattle and horses) when preferred prey is not available. Interestingly, such animals seem to be immune to the lycanthropy that these dark creatures spread.
While werebats do look upon humans and demihumans as animals to be devoured, they are not cruel or evil in their attacks. They simply regard such beings as having a lower place in the food chain. Werebats will, typically, refer to themselves as “predators of the night”.
Very little information about werebats is actually presented in 3e's Monsters of Faerun... in fact, just three sentences of fluff are interspersed in all the crunch, quoted below:
3e's "Lost Empires of Faerun" simply repeats what Monsters of Faerun said.
The 5e version presented in Dungeon of the Mad Mage is not much better, frankly, with a single small paragraph of fluff - but then, this is standard for 5e therianthropes. This version stats that most werebats are infected goblins, and that goblin society shuns them and pushes them to their periphery due to their voracious appetites; 5e werebats need 1 pint of blood per night to stay strong and healthy.
In Dragon Magazine #266, the article "Dragon's Bestiary: Giant Lycanthropes" revealed that voadkyn, or "Wood Giants", are one of the only two species of giant with a true lycanthrope subspecies. This is the Shadkyn; a voadkyn version of the werebat. Shadkyns resemble pale and skinny voadkyns when in their giant form, but have the ability to become mobats (Huge sized carnivorous bats) or a monstrous voadkyn/bat hybrid, resembling a smoky-colored voadkyn with bat-like ears, vampire fangs, bat wings for arms, and prehensile claws for feet. 75% of infected shadkyns only have access to one of the non-giant alternative forms. Shadkyns can infect both humanoids and other voadkyn with their bite; a non-voadkyn becomes a normal werebat with the shadkyn's smoky coloration.
Ability-wise, shadkyns are basically identical to AD&D werebats, just bigger, stronger and tougher.
Shadkyns live in tribal groups, occupying a similar niche to voadkyns - unlike their non-therianthrope kinsfolk, though, shadkyns are voracious carnivores. Farms within shadkyn territory suffer frequent raids, and a distinct lack of large herd animals such as cattle can be one sign that a traveler has entered shadkyn country. Shadkyn tribes are savage bands, ruled over by the largest and most powerful of their ilk, who reigns with a brutal fist; the tribe lives only to breed and feed, consisting of 1d12+3 males, two females per male, and 2d6 children - the weak or elderly are often cannibalized by the rest of the flock if food is scarce. Tribes frequently (60% chance) keep a flock of 1d10 normal werebats as scouts and servants.
Two factors limit shadkyn numbers. Firstly, only one child is produced per pregnancy - furthermore, 5% of these shadkyn children are born with access to only one alternate form (usually the hybrid) and another 2% can't shapeshift at all, resulting in their being driven from the flock to become bitter recluses. Secondly, shadkyn and voadkyn despise each other, and are constantly warring with one another.
Despite that, the two races can interbreed. The product of such a mating has a 50% chance of being either a shadkyn or a voadkyn, and voadkyn children born to a shadkyn parent have a 50% chance of being "lesser shadkyns" (infected werebat voadkyns).
Fusing the primal thirst of the ravenous bat and the unique abilities of individual humanoids, the werebat is a hybrid creature constituting both bloodlust and cunning. As opposed to vampires, who share some similar abilities with werebats and are often confused with them, these lycanthropic beings are often more savage in their behavior and far less calculating than the shapeshifting undead. As though to prove a point, some werebats go out of their way to take down powerful vampire lords and commandeer the vampires’ higher position—though many also become slaves to such undead after underestimating their prowess.
Natural werebats typically look like normal members of their race, though they often have dark hair, slight frames, severe features, and slightly pointed ears. They typically stand slightly taller than normal for their race, but weigh significantly less.
Ecology: Werebats exalt in the freedom of flight and delight in the taste of flesh. Whereas some lycanthropes try to maintain some sense of humanity while living with their condition, werebats are less inclined to do so and tend to abuse their powers. Their hunger for blood and the chaos often resulting from such impulsions tend to make wholesome living difficult for werebats, and so most simply give in to their bestial natures.
Those who wish for a less gruesome and more respectable lifestyle are in constant struggle with forces both internal and external to themselves. Natural werebats can control their primal urges, but are subject to the corrupting atmosphere that is werebat society, always under pressure to submit to the influence of a werebat master. Afflicted werebats have it far worse, their bodies in constant conflict with themselves in addition to the external forces urging them to give in.
One of the most telltale signs of a werebat is blindness—about half of natural werebats are born with poor vision and need strong spectacles, and some are even completely blind. They make up for this deficiency with other heightened senses, however, and possess sharp hearing as well as strong senses of taste and smell. In cultures where it does not behoove one to have a lycanthropic background, werebats with poor vision tend to simply go without glasses, as their keen ears are more than able to compensate.
Of course, the most obvious sign of werebat lycanthropy appears beneath the full moon, when an afflicted werebat cannot help but transform into its bestial shape. Werebats in animal form are far more savage looking than average bats, and resemble their dire cousins to a greater extent.
Habitat & Society: Werebats possess a pack mentality akin to their bestial kin’s, and are able to fly in large, coordinated packs and execute complex maneuvers easily and agilely. This instinctual group dynamic manifests itself in both lycanthropic and humanoid form, the surrounding society reflecting this pack mentality in legal as well as civil configuration. Entire packs of werebats often live in close proximity to one another, and sometimes even entire towns fall to the power of the winged lycanthropes.
Almost always serving a higher master and subscribing to an unspoken understanding of “one for all,” werebats place great importance on meetings and gatherings, holding such events at barren locations such as caves and abandoned castles where the horde will be undisturbed. These gatherings are largely ornamental in purpose and merely provide the afflicted individuals with some sense of unity rather than being a means to any constructive end. Nevertheless, it is a great taboo in werebat culture to show any disrespect toward collaborative efforts or to each other during assemblies, and any infighting is met with harsh punishment.
Turning an individual into a werebat is not ritualistic or organized by any means, unlike other facets of werebat culture. Werebats themselves feel indifferent about transforming unaffected individuals into afflicted werebats; the disease is spread more often because a werebat doesn’t have enough time to finish slaying her victim before she is caught mid-act or her prey has otherwise escaped her, carrying a cursed scratch as a memento of the occasion. Only later does the individual realize what has happened, and usually too late. In paranoid societies, the horror upon realizing one’s own transformation is usually matched with self-loathing and sometimes even drastic measures such as suicide—for in certain regions werebat-hate is so strong that it is easier to simply end it oneself than face the imminent and almost always malicious persecution of one’s peers.
Old World of Darkness
In Werewolf: The Apocalypse, werebats, or camazotz, are one of the extinct Changing Breeds that the Garous tried to wipe out during the War of Rage.
They were originally Gaia's messengers, carrying knowledge through the Deep Umbra and coordinating among the Breeds. Their patron, Bat, was particularly close to and loving towards his children. Their role as messengers made them very good at running away and navigating hidden places without being caught, which unfortunately just meant that it took more than one horrible genocide to completely destroy them.
Their near-extermination during the War of Rage, which did extinguish all European camazotz, cracked Bat's mind, spawning two personalities; one devoted to Gaia, the other to vengeance and the Wyrm. Most of the survivors of the War of Rage were later hunted down by the Black Spiral Dancers, and then all of those survivors fled to South America, where Shadow Lord conquistadors mistook them for Tzimisce vampires, given their bat-like warforms and blood magic Bat taught them, and killed them off completely.
After that, Bat went completely himshit and his Gaian aspect was wholly subsumed as he gave himself over totally to the Wyrm. To their credit, the Shadow Lords eventually realized the utterness of their fuckup, and the descendant of the hunter who slew the last camazotz has devoted himself to undoing his ancestor's mistake, in recent times even freeing an aspect of Bat from the Wyrm's grip. And there are rumors that a few camazotz survived even this out in the deepest depths of the Deep Umbra, occasionally dropping off information at old dead-drops to aid the other Gaians, though if so, they've understandably had enough of this shit and never show themselves to any other Gaians under any circumstances and no expedition to locate them has ever succeeded.
They reproduced like the corax, binding a spirit to a human child via a complex ritual that could fail at many stages, further limiting their ability to survive and making them vulnerable to population devastation. Also like the corax, they had no metis; the ritual automatically failed if attempted for the child of two camazotz.