Wolf Link is an alternate form of Link, which he transforms into in The Legend of Zelda: Twilight Princess. When Link enters an area shrouded in Twilight, he transforms from his normal Hylian form into a sacred beast. As a wolf, Link is unable to use items and has lower defenses, but gains enhanced senses and the ability to talk to animals. In this form, Midna can ride on his back to assist him in combat and open certain doors. Interestingly, Midna is visible in Wolf Link's shadow even when she is not riding on his back.
It seems that when Link transforms into this form, he somewhat gains the characteristics of a wolf such as biting his opponents, digging, growling and causing allergic reactions to others.
Most human and Hylian characters in the game react with fear to Link's wolf form. Exceptions to this include Coro, Jovani, Ashei,Agitha, Iza and the Postman. Ones that have a connection to him, such as Zelda and the Light Spirits, easily recognize Link is not actually a wolf. 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. Many other animals give hints that they know who Link really is.
Upon entering an area shrouded in Twilight for the first time, Link is abruptly transformed into his wolf form. The strain of the transformation renders him unconscious, leading to his capture and imprisonment in Hyrule Castle. During his imprisonment, Link meets Midna, who helps him escape and requests his aid in locating the pieces of the Fused Shadow. However, in order to return to his Hylian form, Link must restore the Light Spirits, eliminating the Twilight from their respective regions.
Later in his quest, Link is hit by Zant's Shadow Crystal, and is turned into a wolf by its evil magic, which prevents the Light Spirits from restoring him. Link acquires the Master Sword, the blade of evil's bane, in order to break the curse, expelling the Shadow Crystal from his body. Using both the Shadow Crystal and Master Sword, Link can shift between his Hylian and wolf forms at will from this point on. However, Midna will tell him not to do this where other people could see them in order to prevent a panic. With his wolf form freely accessible, Link can use Twilight Portals at will and dig in various areas outside of the Twilight. Shadow Crystal Fog found in theTwilight Realm will also force Link into his wolf form, preventing him from turning back into a Hylian until he exits the fog.
Wolf Link is an essential form to knock down Dark Beast Ganon in order to expose his weak point. It is unknown if Link can still transform into Wolf form after the battle, especially since he later returned the Master Sword into the Temple of Time.
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, during which Midna projects a circle of shadow around Link, who can move while the circle is active, albeit rather slowly. Any enemies caught within the radius of the circle at any point will be "targeted" and surrounded with a crackling orange energy. 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 Beastsat the same time, preventing them from resurrecting each other. After defeating a group of Shadow Beasts, Wolf Link is able to utilize the Twilight Portals they leave behind in order to warp between areas.
Wolf Link can also learn various scents, using his enhanced senses to track the person or object to whom the scent belongs. 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, a good way to save money. He is also able to dig and communicate with most benevolent animals.
In certain areas, Wolf Link can use his superior jumping ability to reach places he could not normally reach in his Hylian form, provided he has Midna's assistance in guiding him to a safe foothold. Unlike his Hylian form, Wolf Link is not slowed down when moving through deep snow.
During Link's first transformation, his Triforce mark glows briefly, possibly implying that he is in possession of the Triforce of Courage, and that its power may be the reason he is transformed into a wolf, rather than a spirit, as do most beings exposed to Twilight. This would also explain how Princess Zelda existed in the Twilight World, as she carries the Triforce of Wisdom. If this is the case, it is unknown why Link became a wolf instead of keeping his regular Hylian form. It is questionable why he would even turn into a wolf in the first place, although it should be noted that the Hero's Shade (who is the Hero of Time and Link's ancestor) also has a wolf form, which could mean it's actually hereditary in nature.