Impa

Impa (インパ) is a recurring character in the Legend of Zelda series. She typically serves as a nursemaid and/or bodyguard to Princess Zelda and often offers guidance to Link.

The Legend of Zelda
Impa is an old, but dedicated nursemaid to Princess Zelda. The two share a great relationship, and she almost considers Zelda her daughter, and would do anything to protect her. When Hyrule Castle is attacked by Ganon, the wounded Impa escapes to find a boy with enough courage to save Hyrule. Stumbling across Link, Impa tells him he must find all the pieces of the Triforce, and save Princess Zelda.

Zelda II: The Adventure of Link
Impa is the nursemaid of the Royal Family of Hyrule. Impa knows more than anyone could imagine and it is she who explains to Link his destiny. The Legend of Zelda was passed down from her family to keep it safe. Upon seeing the Triforce on Link's hand, she showed him where the princess was asleep in North Castle. She then told him of the legend of the Great Palace, the location of the Triforce of Courage. She gave Link six Crystals to place in the six palaces all over Hyrule to then gain access to the Great Palace and awaken the Princess.

The Legend of Zelda: Ocarina of Time
Impa makes her biggest appearance, as the loyal protector of Princess Zelda, and one of the Sheikah left in Hyrule. Unlike in other Legend of Zelda games, including Zelda: The Wand of Gamelon, Impa is much thinner and probably younger. She is a great asset to the Royal Family and she has sworn to protect Princess Zelda.

After Link talks with Princess Zelda, Impa appears and teaches him "Zelda's Lullaby" and help him to get out of Hyrule Castle, also explains to Link that he should go to Kakariko Village, an early Sheikah town that where she was born and raised, and she opened to the poor folks. When Ganondorf attacked Hyrule Castle Town, Impa helped Princess Zelda escape on a white horse, and the princess threw the Ocarina of Time to Link. It is possible that Impa taught Zelda the ways of the Sheikah, so she could hide herself from Ganondorf as Sheik.

After Link awakens after having been sealed within the Temple of Light for seven years after opening the door to the Sacred Realm and eventually defeats Bongo Bongo, the boss of the Shadow Temple and awakens Impa as the Sage of Shadow. She adds her power to Link's by giving him the Shadow Medallion. Impa and Princess Zelda aid Link in his final battle, sealing away Ganon to the Sacred Realm.

The Legend of Zelda: Oracle of Ages
Impa is the trusted nursemaid of Princess Zelda. Impa, sent by Zelda to bring Nayru back to Hyrule for protection, meets Link when she finds she cannot move a large rock with the Mark of the Hero upon it: Link moves this with ease. However, Veran, Sorceress of Shadow, had possessed Impa. Veran transfers herself into Nayru, leaving Impa's body. After Nayru is kidnapped, Impa puts all her trust in Link to save Labrynna. This version of Impa is younger than her original and animated appearances, but she is presumably older than the Sheikah Impa of Ocarina of Time and sports a substantially heavier build.

The Legend of Zelda: Oracle of Seasons
Impa is the trusted nursemaid of Princess Zelda, and she has been sent along with a a small group to bring Din, the Oracle of Seasons away from the dangers that threaten her in Holodrum, and take her back to Hyrule. However Din is captured by General Onox, and Impa puts all her trust into Link to save her, as he bears the mark of a Hylian hero. This Impa is the same one as in Oracle of Ages.

The Legend of Zelda: The Wind Waker
While Impa did not appear in The Wind Waker, one of the stained glass windows in Hyrule Castle's basement depicted her with the Sheikah emblem over her.

The Legend of Zelda: Ocarina of Time manga
Impa in the Ocarina of Time manga has some different aspects in story. Link first meets her at the market when playing with the disguised Princess Zelda. When Ganondorf attacks the Castle, Impa is seen attacking some Stalfos with a kodachi. When Link is an adult, he goes to Kakariko Village and Impa trains him and pierces his ears as a traditional rite of passage of the young male Sheikah.

Later in the story Sheik reveals that Princess Zelda wanted to infiltrate as a minion of Ganon. Impa decides to solve this by transforming her into a male Sheikah, and explains to the Princess to tell Ganondorf that she/he left Hyrule because of the Royal Family's betrayal but he has returned due to the possible collapse, Sheik explains this to the King of the Gerudo and gained his confidence.

Valiant Comics
Impa is Princess Zelda's nursemaid. She is very prophetic and knows much about the land of Hyrule. She is the one who warns Link not to leave the North Palace on the day Ganon attempts to invade the castle. Impa is also the one who tells Zelda that the Triforce disappears for a full day every decade.

The Hero of Time
In this fan film based on Ocarina of Time, Impa is Princess Zelda's nursemaid. She believes Princess Zelda's dreams are prophecy and when Ganondorf attacks Hyrule Castle, she helps Zelda escape.

Trivia

 * Impa in the official artwork of the Oracle games has red eyes, implying that she is a Sheikah.
 * Impa is the only true confirmed Sheikah in all the series; Sheik is Princess Zelda's alter-ego and the other characters theorized as Sheikah are not confirmed by Nintendo.
 * It is implied that the Impa from The Legend of Zelda and Adventure of Link is Hylian due to the fact that she doesn't have red eyes; however, this could be only a case of retcon by Nintendo.