Wolf Link

Wolf Link is an alternate form of Link, which he is transformed into in The Legend of Zelda: Twilight Princess. When Link enters the Twilight Realm, he is transformed from his normal Hylian form into a sacred beast. As a wolf, Link is unable to use items, but gains enhanced senses. He can learn various scents and then use his enhanced senses to track the person or object to whom the scent belongs, as seen with Ilia's scent. While inside the Twilight, Link can use these senses to give him a clearer view of the surrounding area, but doing so impairs his long-distance vision. This also allows him to see in dark areas which would normally require a lantern. He is also able to dig and communicate with most animals. In this form, Midna can ride on his back to assist in combat and open certain doors.

In certain areas, Wolf Link can use his superior jumping ability to reach places he could not normally reach in his Hylian form, but only with Midna's assistance guiding him to a safe foothold. Unlike his Hylian form, Wolf Link is not slowed down when moving through deep snow; this is valuable when traveling up Snowpeak and traversing the ruins, where the snow can become so deep it forces Link to change into a wolf. Wolf Link can perform attacks with his teeth and claws, as well as lunge nimbly toward enemies, although these attacks are not as powerful as those he can perform in his Hylian form with a sword. However, with Midna's help, Wolf Link can perform a special attack; Midna will project a circle of shadow around Link, who can move slowly while the circle is active. Any enemies touched by the circle (even if they leave it afterward) will be "targeted" and surrounded with an orange mist. Link can then lunge with great speed at each targeted enemy, hitting one after another in rapid succession as well as damaging any other enemies in his path. This attack is strong enough to defeat many types of enemies in a single hit. This is useful for defeating a group of Shadow Beasts at the same time, preventing them from resurrecting each other. Link can use the Twilight Portals, which appear after killing Shadow Beasts, only in wolf form.

It is later revealed by Midna that the Twili believe in a divine hero who would become a sacred beast to help them. This is perhaps the reason Midna forms a partnership with Link. The Light Spirit Faron tells Link that his turning to a wolf when exposed to Twilight, instead of a spirit like most Hylians, is a sign that the powers of the chosen one rest within him. This may refer to the Triforce of Courage, which is strongly implied to be held by Link.

Wolf Link retains Link's blue eyes and pierced ears, as well as the Triforce symbol on his left paw. The shackle that also chained Wolf Link to the prison in Hyrule Castle remains on his left foreleg.

Later in the adventure, Midna can freely change Link into a wolf once the duo has access to the Master Sword and an evil artifact of Zant's. However, she will refuse to do this where other people could see them because it "might scare someone" or "cause an uproar". Link can thus use Twilight Portals freely and dig in various areas outside of the Twilight.

Most human and Hylian characters in the game react with fear to Link's wolf form. The exceptions to this are Coro, Iza, Barnes, Rusl, Ashei and Agitha. The Postman is not only unafraid, but even recognizes Link in wolf form. Interestingly, Queen Rutela also seems to recognize that Link is actually a Hylian, during his first visit to Zora's Domain after thawing it out. Even Epona is capable of deducing Wolf Link's true identity, whether she saw the transformation or not.

Theory
It is possible that Wolf Link's teeth are infused with the power of the Master Sword, once Link acquires it. For example, when fighting Ganon, Link can either attack Ganon with the Master Sword in Hylian form or attack with his teeth in wolf form to do damage. However, if Link attacks with the Ordon Sword, Ganon merely rolls over and resumes charging around the room, unaffected by the attack. This may imply that both the Master Sword and Wolf Link's fangs have the power to repel evil, though this could simply be a mistake on the developers' part, such as a case of inconsistent planning.