Arch-Mage Shalidor, sometimes referred to as Archmagus Shalidor, was a famous Nord Archmage and powerful wizard who lived during the First Era. He created the Labyrinthian in Skyrim, the mage sanctuary of Eyevea, and his personal compound of the Fortress of Ice, near Winterhold. Shalidor was said to have a vast knowledge of the workings of Magicka that few have ever known.
Feuds with the Dwemer
Shalidor once fought the Dwemer of the Rourken Clan. During their march to Hammerfell, the Rourken Clan clashed with Archmage Shalidor in the Battle of Rourken-Shalidor. The powerful Dwemeri artifact, Spell Breaker, a shield that could reflect any oncoming spells, saw action in the battle.
The Archmage Shalidor was well known for his spell Shalidor's Mirror, which was a ward capable of reflecting offensive spells back at the caster. It is speculated that Shalidor created the spell after his battle with the Rourken Clan, trying his best to emulate the effect of the Dwemer shield, Spell Breaker. Shalidor was also known to put a large amount of effort into researching the dragons that once roamed Skyrim.
Most of the research and writings that Shalidor wrote while in Labyrinthian were lost to the ages, but some of what he wrote is still out there. During the Fourth Era, the College of Winterhold attempted to seek out more of Shalidor's writings to expand The Arcanaeum, improve the arcane skills of the members there and to help the college expand and improve as a whole.
It should be noted Shalidor loved his research more than his wife, Ulfsild; as shown in one of Sheogorath's oblivion realms, his wife repeatedly questions him about his time and research and eventually leaves him due to "no communication." 
Shalidor was a prominent advocate in a movement to keep magic out of the hands of the common people and instead enact higher standards amongst mages. These beliefs are often credited with bringing forth the creation of magic academies such as the Mages Guild. The Labyrinthian was known as the Archmage's testing ground and it still exists into the Fourth Era. While Shalidor was in Labyrinthian, he heavily studied magic and the arcane arts, researching, writing, and experimenting more than anyone could imagine possible. He is believed to have constructed the Labyrinthian by himself and use it to hold an artifact called Glamoril, the secret of life, which was said to be stolen from Akatosh himself. Some claimed that Shalidor had destroyed the infamous Crimson Book of Skulls, but it was later discovered that the book still existed. Shalidor is also said to have built the city of Winterhold with a whispered spell, though whether this is true is unknown. It is possible that some of his achievements have been hyperbolized.
- The Elder Scrolls: Arena (mentioned only) (spell)
- The Elder Scrolls V: Skyrim (mentioned only)
- The Elder Scrolls Online
- Events of "Fortress of Ice"
- Dialogue of Ria Silmane
- Tamrielic Lore
- Spells (Daggerfall)
- The Library of Dusk: Rare Books
- Shalidor's Insights; translated
- Events of The Elder Scrolls V: Skyrim
- Events of The Elder Scrolls Online; Circus of Cheerful Slaughter
- A Minor Maze
- Dialogue of Urag gro-Shub
- The Order of the Black Worm