Cadance is one of the princesses of Equestria, and the current ruler of the Crystal Empire. She is Twilight Sparkle's old foal sitter, and current sister-in-law upon marrying Shining Armor.
Appearance
Cadance is a pink-furred Alicorn, slightly taller than Twilight, but shorter than Celestia and Luna. Her flowing mane is striped with light yellow, purple, and hot pink colors. Her wings are tipped with purple feathers.
As a princess, she is often seen wearing golden horse shoes, and a crown on her head.
History
She used to be Twilight's old foal-sitter while Twilight was just a filly. Overtime, Cadance fell in love with Twilight's older brother Shining Armor, and she and Shining had a royal wedding within Canterlot. After the marriage, she and Shining moved into the Crystal Empire together.
Season 1
Cadance travels from the Crystal Empire to Ponyville to spend some quality time with Twilight Sparkle, and they visit the Starswirl the Bearded Traveling Museum. Their time together is interrupted by the arrival of Discord, who claims to be sick with the "blue flu" and begs Twilight to care for him because the rest of the Mane Six and Crystal Gems are unavailable for one reason or another.
Cadance demonstrates some of her old foal-sitting skills in dealing with the petulant and demanding Discord. She accompanies Twilight on a search for a flower that Discord claims will cure his illness. Despite the complications that arise, from her being out of practice in flying to fending off a Tatzlwurm attack, Cadance is pleased by the adventure and excitement, having felt that life in the Crystal Empire has become predictable.
Season 7
Cadance, along with Shining Armor were abruptly tasked with taking care of Pink Diamond, and show her around Equestria on request of The Diamond Authority.
My Little Universe II
During the finale, she tried fighting off Grogar in Canterlot to drive him away, but she quickly was overwhelmed by the ram and is then taken as prisoner. She is later seen on the Homeworld ships, displayed as a prisoner with numerous injuries on herself, until the Harmony Gems arrive and freed her. When Sumu first starts expanding and invading the world, she joins the Diamond Authority and the Pillars in evacuating Empire City before fleeing to the Earth Moon Base.