|Hyrule Royal Family|
The Sheikah, also known as the Shadow Folk, were an ancient clan of ninja-like warriors that lived before and during the Hyrulean Civil War. They were skilled in magic and swore to protect the Hyrule Royal Family even after death.
The Sheikah are presumed nearly extinct after the Hyrulean Civil War, as Impa appears to be the lone survior.
Curiously, the Sheikah are known in Terminia, a parallel world to Hyrule. Although none have been seen, the Sheikah Mask of Truth exists there, and a few individuals, like Kafei Dotour, sport the characteristic red eyes.
Sheikah are nearly identical to the Hylians, except for their red eyes. As such, some believe that the Sheikah are, in fact, a genetical offshoot of the main Hylian race.
When Princess Zelda, a Hylian, assumed her Sheikah alter ego Sheik during the Imprisoning War, (s)he was identical to a regular Sheikah down to the red eyes. Her method of assuming such a disguise is unknown, though the sheer realism of the disguise suggests magic.
The longevity of Impa suggests that Sheikah lifespans can extend to more than a century.
Like the rest of the races in Hyrule, the Sheikah were created by the Three Goddesses thousands of years before the Imprisoning War.
Initially they lived in seclusion in Kakariko Village, a settlement at the base of Death Mountain. There they practiced their art in secret, and to the other races, the Sheikah envoked mistrust and fear, and in return the Sheikah hated outsiders.
During this time, the Sheikah are assumed to have constructed the Shadow Temple, which seems to play an important role in their culture, though most of the details are unknown.
Hoping to quell the bloodshed, the Sheikah eventually swore loyalty to the Royal Family and became their protectors. Most were killed in the the conflicts between the races, and the Shadow Temple was sealed, and the tear (representing the great loss the Sheikah suffered) was added to the Eye of Truth.
The only survivor was apparently Impa, who, after the war, became the nursemaid to the young Princess Zelda. She was also the caretaker of Kakariko Village, which, after the near extinction, she opened to the public.
Hundreds of years after the Imprisoning War, during The Invasion of Twilight, the Kakariko Village of old was sealed away from the rest of Hyrule, and the remaining Sheikah were presumed dead. An old woman named Impaz, however, had red eyes and claimed that she was descended from Impa.
The Sheikah, like the Hylians, possess a keen magical sense.
As suggested from their artifacts, the Sheikah had the ability to see the truth; in other words, their keen eyes could show them the difference between truth and illusion.
They were also skilled in the Sheikah arts, and when departing a location they seemed to disappear entirely - just a bit of their reported combat skill.
Legend of Zelda Online
In the Legend of Zelda: Online, they are seen as one of the selectable races from the Hylian selection. They are fast warriors and are good with magic; however, they are not as strong as the other Hylian races.