Werewhatevers are pretty decent foes, though they are accursed with the problem of 'why can't lycanthropy be used as a power-boost for my character' that has plagued GMs since their inclusion. The excuse of becoming evil even while not in wereform does not dissuade some characters, is sorta suspect in general, and doesn't even apply in all cases since werebears are chaotic good, and wereboars and tigers are at least neutral.
The curse is simultaneously easy to get (taking 50% of HP damage or more from a lycanthrope) difficult to remove (requiring either a 1/4 chance of belladonna curing it but poisoning the character for 1d4 days with a 1% chance of death) or a level 12 cleric to cast cure disease within 3 days of infection. So the question of what to do if a player is infected is a common one.
As far as the different varieties go, Werebears can cure disease and are probably a reference to Beorn of Lotr, perhaps combined with the figure of Bödvar Bjarki. They also work with brown bears, which seems less likely than working with other infected but whatever.
Wereboars are the most inexplicable to me. They are neutral but foul tempered and likely to attack, and I am not at all sure what they might be a reference to mythologically.
Wererats are suprisingly tough with 3HD and are almost certainly a reference to Hisvet and her ratty friends from the Fritz Lieber books of Lankhmar, and are a staple of the urban sewercrawl.
Weretigers being 'most often female' makes me think they're likely a reference to a specific character rather than a mythological category. Hantu Belian are a malaysian possibility of origin inspiration, but it seems less likely. Or maybe the artist just really wanted to draw tiger teats in the art, idk.
Finally, werewolves are obviously derived from mythology and hammer horror films (as I guess from the artwork) and are most divergent in that they are quite pack-oriented as opposed to the lone accursed fellow-3d6 werewolves being the average number-appearing, rivaled only by the 4d6 wererats.
All in all, there is a disconnect from the desire to have lycanthropy be an alienating, isolating curse, and the apparent small gangs of these creatures getting up to a wide variety of alignment-appropriate activities and social interaction. They're plenty dangerous to adventuring parties with multi-attacks and a tenacious curse. One wonders if slings loaded with the incredibly numerous silver coins would provide ample defense even to peasantry against such threats- even in a copper standard, where money is 100 times more dear than the gold standard, silver is not some exotic metal to be carefully sought after and hoarded, it's just something you could presumably get from the coffers of any business, so their weakness doesn't hold the same problem as the modern werewolf film.
All in all, I think 'the curse of the werewolf' idea doesn't hold up well in a D&D universe in terms of logistics or implied setting... it's either a known problem with known solutions and is thus free of any supposed horror, or too easy to manage and suddenly it's a supersoldier serum, or it's a campaign ending blight akin to a zombie apocalypse.
Sunset Realm Lycanthropy
There are several types of shape-changing beast-folk in the realm
Firstly are those of inhuman ancestry, manifesting not as the more typical permanent hybrid form, but as having multiple forms + a 'best of' combination. The 'immunity' to weapons comes from the ability to heal wounds by transforming to some degree- limbs may not regrow, but wounds will close. Wounds inflicted by silver may carry over between forms, the lawful metal refusing chaotic undoing of its deeds, or serious injuries or bindings of silver may prevent transformation all together until healed/removed.
This form of beastliness is not contagious, but it is heritable. Transformation is typically based on stress or focused will.
The second form, that of Curse, occurs thanks to possession of a human body by an animal spirit. The transformation is hideous here, as one form is distorted, broken, then 'healed' into another by the unnatural vigor of two souls within one body.
Horrible crimes against animals may cause vengeful beast spirits to possess the offender, turning them against humanity as vengeance-by-proxy. This is quite unlawful, which is why silver is effective. The other main source would be being cursed by the gods- Our Lady of Gardens inflicts this curse against those who completely defile and disregard her society, granting them an unsightly form to match their behavior, and allowing others to hunt them as they please. This curse is not given lightly- Our Lady must cooperate with her rival Murulu, who is lord of such corruption and transformations, or with Lumar, who can mimic Murulu's powers, and explains the association with the moon such beast curses have. Lumar may inflict this curse whilst mimicking Our Lady as well, though the mysterious goddess likely does so with ulterior motives like the beast accidentally burning down a library or slaying those who know secrets when the moon arrives. Either way, the beast-soul assigned to torment the accursed is assigned as punishment, so attempts at harnessing the beasts powers are doomed to failure as the beast will thwart the accursed in every way possible. Typically, this curse is not contagious when god-granted, unless the punishment is meant to spread to the allies of the accursed as well. However, especially in the case of punishment by beast-souls, the soul may splinter itself into nightmare fragments to propagate and may well be a contagion.
Either way, the curse can only be lifted by mollifying the gods or the angry animal spirits, so there is no one-size-fits-all cure besides death by silver.
The third form, that of Blood, is a disease, of sorts, a contamination borne of the combining of Moon Blood and the blood of beasts, then introduced to the human form via injury or improper blood transfustions not sanctioned by the Sanguine Church of Vint-Savoth. This form taints the mind with bloodlust, and deforms the body with foul mutations that are related to the animal blood in question, but are ultimately alien in origin due to the source being the Blood Moon. If full transformation occurs, there is no going back- that person's soul is gone at best, or trapped within a raging monster of the Blood Moon at worst, hoping to save its comrades if it can wrest back control for even a second.
Such beasts are best slain by fire, silver, or massive bloodletting to drain the corrupted blood from its host.
As far as location of the 'standard' werebeasts goes...
5th age Oroboro had the first form of Werewolves in the hills, a clan sworn to oppose the villainous wizard who lives in those parts. They may date back to the 4th intersolar period, where humans seeking to survive the sunless darkness mixed bloodlines with wolves. It is unknown if they survived the Enlarge Wars, but they likely would have been forced to become more urban.
4th Age Phillipston was initially human, but was overrun by wererats of the accursed sort after the power of the Riikhites and Mokkhites was broken. These wererats date back to accursed experiments by Sarkomand early 4th age. By the 5th age though, the curse had weakened such that the ratty population was essentially the non-dangerous 1st variant, though prejudice lingered for generations, leading Phillipston to be fairly insular. The 6th age Phillipston Anomalous Subsurface Control Committee, or PASCC, was also known as the Rat Race due to high numbers of rat-folk signing up for the dungeon control and exploration teams.
4th age Yuban "werewolves," actually weredogs known as Cynocephali, were sacred, rather than accursed warriors of Yuba who fought back against Riikhite Mercia, and were demonized for it. In the 5th age imperialism had diminished, but Cynocephali still had enemies in the form of the Cat Lords or Rakshasa, who created accursed weretigers to serve as a counterforce in bloody internecine conflicts as Yuba tried to reunify after being broken in the 4th age. By the more peaceful 6th age, werebeasts had receded into being more of the first variety than the supernatural variety, with those who engaged in battle frequently forming public color-coded super teams.
While Vint-Savoth was scourged by the Blood Moon even before it had a name or was settled, and as such has every variant of the 3rd type of werebeast and more, it may be worth noting that even in the 6th age after the Blood Moon was felled and largely contained, werepigs of the 'angry beast soul' variety rose up against factory farming as horrible chainsaw-wielding pig-men until, as happened in Prince's Spit with the Three Tusk revolts, the inhumane practice was ended for good.
Actual Rules I use for Lycanthropy
If forced to roll on the Death and Dismemberment table by a contagious-type werebeast, lycanthropy is contracted on a failed save. If killed, one may choose to contract lycanthropy instead to save ones own life, though it cannot be cured save by magics comparable to that of raising the dead in that case.
Ancestry Type- This type would be run as a 'race-as-class,' perhaps multiclassed with a more standard class. The Spook from Esoteric Enterprises would probably work, with Grit HP regenerating quickly due to transformations clearing wounds, and Flesh HP being struck directly by silver weapons.
Transformation occurs upon the curse's trigger- moonlight, witnessing appropriate animals being eaten by humans, etc etc, and upon periods of great stress, physical or mental- failing a save vs fear or being reduced to low HP, for instance, likely trigger a transformation into the appropriate statblock, healing all non-silvered damage and, bursting out of armor, backpacks, clothes, etc and destroying them.
Characters with equal or fewer HD than their beast-form cannot control it or remember what they did in any detail. The beast is typically unnaturally violent.
Characters with more levels/HD than their beast form can control themselves to some degree and can make saving throws to prevent themselves from attacking allies while transformed, and can act with some direction beyond 'accursed rampage.'
Characters with at least double the levels/HD of their beast form are, against all odds, able to go beastmode at will and can control themselves, though the transformation lasts until next dawn. Essentially, it is only a weird superpower at this point.
Magic items meant to aid in control, or perhaps unusual mental stat modifiers, may count as bonus or malus HD for purposes of controlling oneself. Each year survived with the curse probably adds a 'virtual' HD for purposes of controlling oneself as well.
This is more of a corruption track, as once transformation occurs, the soul either leaves, or stays within the body, able only to take control for a total of 1 round per level ever before control is lost forever.
Every time corruption is gained and corruption > level, a save vs scourge must be made the next time great stress is felt, mental or physical. Failure indicates transformation into a beast of HD=Level+Scourge.
Scourge Track- The stages roughly corresponds to what percentage of blood is pure moonblood, as opposed to what percentage is corrupt beast blood.
0- Unsullied- No exposure to the scourge
1- Acceptable levels. Scourge never goes below 1 after initial infection barring incredible magics or mad science.
2-4- Hunter-Acceptable Levels- Scourge Level provides various advantages if the right techniques are utilized. The Church issues tags confirming blood status to sanctioned hunters.
5+- Public Menace Levels- Berserk bloodlust clouds judgement. Must make a saving throw to not consume blood or stop attacking targets in melee. Mild physical transformation such as elongated hair, teeth, nails, eye color changes, mucular growth, etc. It is not unheard of for very skilled hunters to lapse into this state on particularly long or horrible hunts, and rumors abound of secret church forces who have tags sanctioning blood corruption of 5% and higher.
Common Scourge Sources
+1 Skin contact with scourged blood. First-time only.
+2 Internal contact (ingestion, wound contamination, transfusion) with scourged blood of higher HD source/Scourge level than your own.
+1 Making a Death and Dismemberment roll. Only applies if you have at least 1 Scourge. Counts as 'great stress' so immediately check if a possible transformation is in order.
-1 Monitored bloodletting and transfusion by the Sanguine Church over the course of a week. Counts as 'great stress' for potential transformation, though the Church typically euthanizes transforming unfortunates before they get out of hand.