Beast Form (Skyrim)

Beast Form is a power gained during the quest The Silver Hand, after completing the blood ritual with The Companions. This once-daily power grants the ability to turn into a werewolf for a short time. The Ring of Hircine allows Beast Form to be used as many times as desired per day.

After becoming a werewolf, the Dragonborn cannot obtain Rest bonuses (excluding Father's/Mother's Love) unless cured of Lycanthropy. Kills in Beast Form will be counted as "mauls" in the general statistics. Also listed are the number of days passed since becoming a werewolf and the number of transformations into Beast Form.

On its own, Beast Form fades away in 150 seconds. Feeding on the corpses of humanoids increases the duration (30 seconds per feeding, 15 seconds for animals after acquiring the Savage Feeding perk), and replenishes health.

While in Beast Form, health will not regenerate passively; feeding is required. Spells such as Oakflesh, Muffle, Flame Cloak, Stoneflesh, summon spells, and racial powers such as Night Eye will remain in effect for their normal duration when in Beast Form, but cannot be recast. A werewolf can increase survivability by howling, causing enemies to flee, or consuming health regeneration potions or foods before transforming, as their effect will still be active in beast form. Higher level opponents may not be affected by the howl.

Dawnguard
If Beast Form was previously acquired but then was lost, talk to Aela. She will have a dialogue option allowing the Dragonborn to regain the gift of the beast blood. She will comment that Hircine usually doesn't restore the beast blood to the fickle, but also states that the Dragonborn has proven worthy. She can do this indefinitely, as long as the player does not cure him/herself of the Lycanthropy in Ysgramor's Tomb (i.e.: If the player loses Lycanthropy due to acquiring Vampirism from Serana or Lord Harkon, he/she can re-acquire his/her Lycanthropy from Aela an infinite amount of times, but if he/she cures him/herself at the Tomb of Ysgramor like Kodlak, Farkas and Vilkas, he/she will never, in the course of the game, be able to re-attain it).

Dragonborn
A pack of werewolves can be found at Frostmoon Crag, southwest of the Temple of Miraak and northeast of the Abandoned Lodge. There, the Dragonborn can meet the leader of the Frostmoon Pack, Majni, who will comment on the Dragonborn's lycanthropy, as well  as explain how they are the last true pack on Solstheim. Afterwords, he can be asked if he has anything to trade. He says that for many years, the Frostmoon pack has guarded a set of rings blessed by Hircine. He offers to sell them, albeit at a very expensive price.
 * Ring of Bloodlust - While in Beast Form, your attacks do 50% more damage, but you also take 50% more damage.
 * Ring of Instinct - When you enter Beast Form, the world around you seems to slow down for 20 seconds.
 * Ring of the Hunt - While in Beast Form, your health regenerates.
 * Ring of the Moon - Increases the duration of your Howls by 25%.

Trivia

 * If the Essence Extractor is in the inventory while in Beast Form]and during Discerning the Transmundane, the menu option to collect blood samples may appear while feeding.
 * Beast Form can be used as a quick form of travel as the werewolf's sprint is faster than a horse and uses little stamina.
 * If a Forsworn Briarheart has his Briar Heart removed, either by pickpocketing or looting before being fed upon, the standard message will appear that a heart has been eaten, and the feeding will count as a regular feeding in every way.
 * The undead cannot be fed upon (vampires and death hounds).
 * It is not possible to feed while swimming. (Floating bodies can be pulled from the water and then fed upon.)
 * It is not possible to level up while in Beast Form.
 * Going into Beast Form does not trigger an autosave.
 * Dead Werebears cannot be fed upon without the perk Savage Feeding.
 * The Sneak perk Light Foot continues to function while in Beast Form.
 * The player will NOT accumulate bounty in cities or settlements if he turns into a Werewolf without being witnessed by anyone (works best if transformation is made outside of city or inside owned house, with no people at least 20 feet away). This allows for easy completion of Dark Brotherhood contacts or otherwise getting rid of unwanted NPCs inside cities with NO penalty. Also works with the Vampire Lord.

Bugs

 * If stuck in Beast Form, use the wait function to skip two to three in-game hours. This will force a return to normal form.
 * In rare cases, during the first transformation the Dragonborn may end up holding a weapon in the right hand while in Beast Form, and will always have the weapon in that hand in during later transformations. The weapon doesn't affect damage. This also applies to torches and will center out on the bottom of the display. The torch will continue to work and emit light. If a staff was held in either hand before turning into a werewolf, the staff may remain equipped and can be used.
 * When trying to feed while in Beast form the body may be searched instead. Can usually be fixed by transforming using the Ring of Hircine instead of Beast Form.
 * Beast form may only last a few seconds, even if bodies are fed upon.
 * The Ring of Hircine might not allow extra transformations.
 * Reanimating corpses that have had theirs hearts consumed will increase Werewolf Perk.