Sirian

The Deity
Sirian is the God of Light and main deity of the pantheon of the Light, he is portrayed as an angelic warrior wielding a sword of pure light, Sirian is the god mostly worshipped by the Order of the Paladin of Stromgarde, also Sirian's Sanctum in the capital city is named after him.

Has been revelaled later on that he wields the power of Holy Light, and the race of Naaru has been created to be a messenger of the Light. Also the Angels, until now believed to be only a tale, are the guardians and protectors of Hyperborea, the home of Sirian and all the other gods of light.

All the paladins and priests who wield the holy light are using Sirian's power.

Sirian's gifts are granted to whoever will follow the light and will be true to it, he is benevolent and can forgive, but will punish harshly who will try to defy his laws, and thus the light.

World of Darkness Rising
As Sirian misteriously disappeared from Azeroth after having finally been released on the world, the world of Darkness has begun, as Sirian's power wasn't anymore strong enough to balance the overwhelming darkness of the Dark God and his minions.

Some tells that if Sirian would be brought back, the Darkness Rising would may be stopped, but it's just a rumor.