I went through and scoured as many primary sources as I could find to write a guide to lycanthropy. I'd love to hear if I've missed anything so I can add it in. This was mostly written with RPers in mind..
Kis' Guide to Lycanthropy:
Hircine’s sphere is the hunt.* The Sport of Daedra, the Great Game, the Chase. He is known as the Huntsman and the Father of Manbeasts.* His realm of Oblivion is the Hunting Grounds, where Hircine pulls in those who have served him to spend the afterlife.* It has been suggested that men and mer are able to choose where their soul spends eternity - suggesting lycans who accept their gift may go to the Hunting Grounds, but a Nord who prefers to go to Sovngarde may go there instead.* However, there are other documents that contradict this, saying Nord lycanthropes will “spend eternity in Hircine's Hunting Grounds, slaves to his unending thirst for blood and the chase, instead of drinking mead and brawling with the heroes of legend.”*
It is not known how Hircine created lycanthropy, but it is widely acknowledged that he was involved. The disease has been recorded since the early Merethic Era, and may have been around earlier but the lack of writing makes it difficult to prove.*
The aspects of Hircine are:
-Alrabeg the Hunter, targets and finds new prey, then brings it back to the hunting grounds.
-Storihbeg the Manbeast, creates more lycans and has a howl that freezes people in fear.
-Uricanbeg the Great Stag, who comes to mate and cull the herd of the weak. The drumbeat of his hooves drives listeners to run with the herd to the Hunting Grounds.
-Gulibeg the Quick Fox, runs hunters in circles to perplex and exhaust them, or runs them right off of a cliff. May teach tricks to those he considers clever.
-Hrokkibeg the Mighty Bear, who seeks solitude and peace and rest after a hunt, but if his rest is disturbed you will be torn to pieces.*
Because Hircine is a representative of the hunt, he represents all aspects of it. From the hunter, to the kill, to the peace and satisfaction afterwards. Worship of Hircine can vary from the less-feral side to the more vicious side, depending on interpretation.* He is also worshipped by people who hunt for a living, or for meals, but aren’t necessarily lycans.* This level of worship - a simple request for luck when drawing a bow, has less of the negative association as an intense level of worship would bring.*
Hircine dictates that the quarry/prey must always have a chance at escaping, no matter how slim. If the prey is trapped, is it not considered hunting.*
A prayer to Hircine:
I lift my weapons to you!
Bless them, and guide them true—
Let the sport begin!
Let the blood spill!
Hunter and hunted,
In a chase to the death!*
LYCANTHROPY AND THE GREEN PACT:
Y’ffre gave the Bosmer their form as mer. Hircine gave them the gift of a second shape.* When Y’ffre made the Green Pact, a clear rule was made to not take on the shape of beasts, and that the form of the Bosmer is sacred.* Any Bosmer (note: not just Bosmer who accept the Green Pact) who changed their form would be condemned back to the formlessness of the Ooze and their names would be scrubbed from Y’ffre’s story, to be replaced by silence.*
LYCANTHROPY AND THE GLENMORIL WYRD:
The Glenmoril Wyrd, or witches, are a Wyrd coven comprised of only female humans and half-breed humans like lamia and hagravens. They’re normally considered reclusive, dangerous and evil - however this mostly seems to be a misunderstanding stemming from different morals. Most of the Glenmoril covens worship Hircine, particularly the less-feral aspects, and may provide a few lucky souls with a cure.* (More information on cures below.) The Glenmoril Wyrd may also have been taught by Hircine how to take on the form of a true wolf, instead of a werewolf.*
Most members of society will believe that lycans are horrific monsters. It is normal for family members to turn against the people they love, if they discover they have become infected with the disease.** It is generally accepted that family members die when they become infected, and the form that remains living is no longer the same person they cared for.* People who actively seek the curse of lycanthropy are safely assumed madmen.*
STRENGTHS AND WEAKNESSES:
-Weak to silver.*
-Wolfsbane petals applied to bones renders them brittle, causing them to collapse.
-Ripened belladonna berries pressed to the veins causes them to shrivel, if it gets to the heart it can cause it to wither.*
-Canis root repels were-bears.*
-Poor sleep. (gameplay: Skyrim)
-Can show physical signs of the disease when in their original form (gameplay: Skyrim)
-Vulnerable to poisons, even weak ones.*
-Increased size - shoulders, arms, fingers and feet all increase in length.*
-Powerful jaws and claws
-Claws act as if enchanted weapons, and are effective against creatures like golems and atronachs who are resistant to normal weapons.*
-Increased height, said to stand three hands taller than an orc.*
-Better fighting skills.
-Increased strength & stamina.*
-Increased sight, hearing and smell.*
-Pelt that reduces pain and adds a resistance to blows from normal weapons.*
-Completely resistant to disease. (gameplay: Skyrim)
-Increased health regeneration when fed or feeding. (gameplay: Skyrim)
Lycans (Possibly specifically werewolves) are often found in packs. The howl can summon other werewolves to them, but also regular wolves and bears, indicating an alliance between lycans and mundane beasts.* There is evidence of war-dogs fighting beside their lycanthrope master when he gives three short howls while shifted.*
Any bite or scratch from a lycan gives the possibility of infection.* The initial infection is called Sanies Lupinus or Canis Hysteria, while the names are interchangeable, the former is more widely-known.* Drinking the blood of a lycanthrope is a more potent means of transmitting the disease, and the conversion is immediate, the transformation happens within moments and is normally intense. (Gameplay: Skyrim)*
Lycanthropy can be cured shortly after infection, but after the first transformation it is significantly harder to cure.* The initial infection can be cured with a simple Cure Disease potion, spell, or by visiting a priest of Arkay* within a three day period, after that the infection has set in.*
In Elder Scrolls: Online, there is a quest in Camlorn to use werewolf blood to cure lycanthropy - however the rest of the recipe was never revealed.*
The most common ‘cure’ is by seeking the help of the Glenmoril Wyrd. It involves the death of an innocent, ripe belladonna berries and wolfsbane. The innocent must be killed and their heart removed by the lycanthrope, then the witches soak the heart in the concoction they made while chanting incantations. The lycanthrope must then put the heart back into the innocent, the witch recites the final incantation and the innocent must be killed by the lycanthrope.*
BLOODLUST & SHIFTING:
Willpower and fortitude seems to be important to how well each individual person reacts to infection.* Some attempt to live a more peaceful life. Believing the gift isn’t meant simply for sport, and that the blessing should not be used against man and mer, or to torment. They use hunting as a way of worshipping Hircine, without giving in to their bloodlust.*
Likewise, there is evidence that hunting on a full stomach dulled the desire to hunt and kill, and granted an increased level of control. This control seems to require an acceptance of the curse as a gift or blessing, and an attempt at understanding it. To suppress and reject it, causes the changes to be more violent and increase in strength.* Similarly, hunger makes a lycan more likely to go feral. In this state, lycans are more likely to to fly into a bloodrage and slaughter anything that crosses their path.*
Alternatively, lycanthropes can embrace their savage side, forming packs to spread their disease and cause mayhem even as non-beasts. Magnar Child-Eater was known to develop a taste for the tender flesh of children, and would seek to devour them especially.* Reachmen are also known to worship Hircine, and are known as being particularly savage.*
Total control is only obtainable through the use of a powerful relic, such as the Ring of Hircine. There is only one of these in existence.* However, lycanthropes are able to maintain some semblance of personality, perhaps recognising items or people that they care about.* Some are able to remember their experiences while shifted, although amnesia tends to be common.*
While it is a common held belief that the phase of the moon has an effect on a Lycanthrope’s transformation, there is no evidence of this directly. While Khajiit have an association with the lunar changes, it is thought that werewolves worship the moon, instead of actually being affected by it.* In Elder Scrolls: Daggerfall, werewolves were forced to shift into their bestial forms on a full moon,* and in Elder Scrolls: Online, the rare mobs that spread the disease only spawn at night on full moons - however there is no evidence in lore to support these gameplay mechanics.
Descriptions on shifting:
“...arms splitting out of his armor, hands stretching into long, clawed talons. His undershirt ripped off, skin sprouting a thick mane of hair along the forearms and chest. A terrible transformation in the face: nose crackling and stretching to form a black snout, mouth ripped open and incisors growing to fangs in an instant. Eyeballs yellowing into a wild glint. A tail sprouting from the base of his hairy back. Saliva frothing from a dropped jaw, now snarling with malice.”*
“...his eyes flash red. He fixed his gaze on mine, stood impossibly tall, and began snarling and thrashing like a madman. It took a moment to realize that he was growing both up and out. Hair sprouted from his form and his rags fell away. As his nose lengthened into a black muzzle and his bones cracked and twisted, I finally started to run. I’d offended a werewolf.”*
TYPES OF LYCANTHROPES*
The most common strain, and can be found in every part of Tamriel.*
Stalk Black Marsh and southern Morrowind.
Found in Black Marsh, the Imperial Province and the wetter parts of Elsweyr.
Found only in Valenwood.
Found in the swampy areas of Valenwood.*
Found in High Rock and Hammerfell. It attacks with both forearms and its long teeth/tusks.*
The most common lycan in Skyrim, but also found in the northern parts of High Rock, the Imperial Province and Morrowind.
Only rumoured to exist. There are no known sightings in lore, but is supposed to exist in the ocean.