My prediction is not so much of the Inquisition story, itself, but rather how things came to be.
The Maker is was a benevolent (and genderless) spirit of the Fade that acted as the Fade's leader (and protector?), until Tevinter Magisters decided to seek the Fade's mysterious leader out in it's home, the Golden City, under the orders of their 7 leaders Dumat, Razikael, Uthemiel, etc. The city's residents are spirits who turned into various demons as a result of the Maker's rage from the Magister's attempt to enter the Golden City. And the Maker itself - in it's rage - turned into a demon as well, and the Golden City turned black as night. The City and it's residents are directly connected to the Maker in some way, hence the transformation into demons and the Black City.
The Magisters found the City black, and called it the Black City. They broke in to see the Maker, battling the newly transformed demons as they went. Many of them were turned into darkspawn upon death, having their souls removed by the Maker. The remaining few Magisters were forced out of the Black City, and turned them into half-demons. It sent them to separate corners of the Fade.
Dumat and the other gods entered the Fade after the initial transformation of the Golden City, whereby The Maker chained them and brought them in a room nearby it's throne room. They were powerless to stop it. The Maker removed their souls from their bodies, and transformed their psuedo-dead husks into dragons, possessed them, and forced them to leave the Fade, into the underground where they were freed of their possession and fell into deep slumber. The darkspawn left the Fade, following their masters, the Old Gods into the Deep Roads.
The dwarves had already been living in the Deep Roads by that time. They were a race of humans who left the surface where the humans had began to evolve, and grew short and stout. They found the land of Thedas, in the underground, where they started their civilisation. Elves, another race of humans, some time later broke away as well, and went to live somewhere else. They also found Thedas, and began to grow tall and benevolent with the help of the oxygen, life-giving trees.
The darkspawn found the dwarves and captured many women and turned them into broodmothers, and together they reproduced with the intent of finding their Old God masters.