Light

History
Light was one of the seven powers that created existence. like its fellow powers, the power of Light was passed down by the sorcerer Osaros and it's fell into the possession of many rulers throughout the realms. one such ruler was the alicorn princess Celestia, who used its immense power to constantly rise and set the sun in her world and keep order as the ruler of Equestria. one other such user before Celestia was a wise wizard who lived in the same universe as the sorcerer. Tirek also had this power, but didn't know about it's true abilities, so he didn't use any of its real powers. Twilight also had this power and was able to use some of its true abilities. the final user of this power was Dante, but it was soon relinquished back to the previous user, Celestia.

Purpose
Its ability is the full control of light and anything relating to it. with this power, the user can draw strength from any light source, even a small glimmer on a reflective surface. this can also endow the user with immense mastery over any and all light magic. its role in existence is to maintain the light of hope and prosperity among the inhabitant of all universes.

Users
Celestia: the current user, who uses this power to raise and lower the sun. she also has access to extreme levels of magic and, even after she sealed away half her power, she still possessed great power. once she did unlock her power, she gained immense strength, speed, and magical power that was able to challenge Dante, who had two ancient powers and his old alicorn power.

Tirek: after he escaped from Tartarus, he took the power of Light from Twilight, who had gotten from Celestia, and he didn't gain any of it's true abilities, but he still grew in strength and magic.

Twilight: after the other princesses gave her their powers, Twilight gained the power of Light and was able to use some of its real powers. among these powers was extremely strong magic, enhanced speed, and the ability to move the sun.

Unknown Mage: after Osaros, the next user of Light was a wise and noble mage, who used this power to promote peace and spread goodness throughout his universe.

Dante: after defeating, and seemingly killing, Celestia, Dante gained all of Light's powers. after this, he gained even more magic and could preform even more powerful version of his spells.