There are seven Old Gods. Scholars agree they may indeed have been real at one point, but most agree they were likely actual dragons -- ancient high dragons of a magnitude not known in the modern day. Some even claim these dragons slumber as a form of hibernation, not as a result of the Maker's wrath. Five have risen as Archdemons, and were only identified after years of argument among scholars. To this day, it is unclear whether the Archdemons were truly Old Gods and not simply very powerful, ancient dragons.
It is said by the Chantry that the spirits of the Fade were the Maker's first creations and were flawed, and thus they were cast out of the Maker's grace. Jealous of the living, it is said these spirits whispered to them in their dreams, telling them they were the true gods and that the living should bow down to them. And so the living did, summoning these spirits through the Veil into the physical world and worshipping them as idols that walked among them. These were the Old Gods, spirits powerful enough that it is said they took the form of dragons, and ruled over the land. According to the Chantry, their worship was the Original Sin. The Old Gods angered the Maker by claiming to be the creators of the world, ying to the living and supplanting the Maker's true place. When furiously, the Maker abandoned the Fade and his ungrateful creations, he cursed the Old Gods who existed in the world of the living, imprisioning them in tombs deep beneath the earth where they would slumber eternally.
Even from their underground prisons, the Old Gods were able to whisper into the minds of men. Archon Thalsian, first of the Magisters, who claimed to have contacted the Old God Dumat, used the blood magic Dumat taught him to attain incredible power in Tevinter and declare himself ruler of the Empire. In return, he established the first temples worshipping the Old Gods, and spread the religion, the dragons becoming equated everywhere with Imperial power. Thalsian also created the Magister ruling class that has existed to present-day, his pupils forming the noble houses. Mages of the Imperial Chantry today claim it is more likely that blood magic was learned from the elves of Arlathan, but there is no evidence to support either theory.
Prior to the beginning of the First Blight, worship of the Old Gods was at its height. Then Dumat rose from his prison as the first Achdemon. The believers felt betrayed that one of their deities would turn against them. Ancient lore states that it was Dumat who created the first darkspawn, but the Chant of Light says it was the darkspawn who created the Archdemon. The tale of the Darkspawn's creation is known as the Second Sin -- the ancient Magisters attempted to open a gate into the Golden City within the Fade. They managed to enter the Black City, but tainted it with their sin, and were cast out as the first Darkspawn. They hid underground and searched for their old master, and tainted Dumat, unleashing the Blight upon the world. It brought mankind nearly to the brink of annhilation, and 200 years before the Wardens finally slew the Archdemon Dumat, ending the Blight.
Worship of the Old Gods diminished through the Second Blight and the rise of the Chantry. Temples were burned down and destroyed, their cults either dispersed, or driven underground, and some -- mostly in Tevinter -- still stand, but were converted to other uses. A few cults still exist, particularly to those Old Gods who have not yet risen, but they are far and few. And the Darkspawn still hunt the Old Gods underground to corrupt them. There have been five Blights, the Blights nearly bringing mankind to the verge of destruction. If the next two inevitable Blights do not manage to destroy mankind, scholars wonder what will happen when the seventh Archdemon falls.
The Old God of Silence, he was said to be the leader and the most powerful. He was the one originally to teach blood magic to the first magister of the Imperium. In -395 Ancient he was the first Old God to be tainted into an Archdemon. He was slain at the Battle of the Silent Fields in -203 Ancient.
The Old God of Chaos. In 1:05 Divine, he rose as an Archdemon to lead the Second Blight, destroying the city of Nordbotten in the Anderfels before the world reacted. He was slain at the Battle of Starkhaven in 1:95 Divine by the Grey Warden Corin.
The Old God of Fire. In 3:10 Towers, he was awakened to lead the Third Blight. Toth was slain at Hunter Fell by the combined armies of the Grey Wardens, Orlais, and the Tevinter Imperium in 3:25 Towers.
The Old God of Chains (Slaves). In 5:12 Exalted, he was awakened to lead the Fourth Blight, completely overwhelming Antiva and laying siege to Hossberg. In the Battle of Ayesleigh in 5:24 Exalted, a combined army from Orlais, the Anderfels, and the Free Marches -- under the banner of the Grey Wardens -- defeated his horde, and the Archdemon was slain by the elven hero Garahel.
The Old God of Beauty. In 9:30 Dragon, he was awakened and led the Fifth and most recent Blight. He was slain a year later by Theron Mahariel at the Battle of Denerim. He was the fairest and most graceful of the Old Gods. It is believed by Tevinters and dragon cultists that Urthemiel fathered a daughter, Urzara. Cults of him, and the two that have not risen still exist, and Urthemiel -- though he is still a prominent symbol of Tevinter today -- has mostly lost his original significance.
The Old of Mystery.
the Old God of Night.