The teory of BOF timeline (teory)
I believe BOF 4 is set in a parallel universe , as well as the Dragon Quarters . At least , it seems more reasonable to me this way .
There is not a truly official timeline, but I think it would be really cool if it were as follows (timeline not in terms of exact games, but a chronology of world history BOF, games included) :
1st - Age the machines , no other races or Brood (or at least, with with infinite power , which emerged at some point) . Myria already exists as a goddess . Probably a long period of civilization for many, many millennia of progress.
2nd - The Apocalypse of the machine age and birth Desert ( wars , causes unknow, probably by an uncontrollable power, cosmic, not from this world) . Myria uses her power to separate continent - remains weak , surviving mortals rebuild.
( some magic occurs in the meantime , creating races , including Brood , whether for technology , either by magic or by some "power" that was born or stopped over the world, cosmic maybe) .
3rd - Brood emerge somehow as well as other breeds , including the demons (probably a mixture of powers of Myria scatered in the separation of continents, existing magic and some cosmic power, who knows) . Myria fears the power of the Brood ( heirs of the power that destroyed the world ? ) And for the next 3 games was trying to destroy them.
4th - Myria generates conflict between the dragons to cause war and destruction among them . A hero stands up with his friends and imprisons her - before the BOF event I.
5th - Myria still has power even imprisoned , manages to convince the dragons free her and do war again - events BOF I. We all know what happens .
6th - With the success of Ryu BOF1 Myria is very weak for a long period . Could not tell if the demons are BoF2 products Myria or not ( rather not, would be a worthy villain in a sequence) , preferring not. With the powers of Myria weakened , the demons are gaining ground , forcing the Dragons ( already well diminished in number ) to assume responsibility for guarding them . Events BoF2 , we all know how it ends ( and the demons are not decimated ) .
7th - Much later , Myria resumes her power and then decides to make a direct crusade against Brood with her guardians . The members of the Brood , perhaps knowing their devastating power , perhaps knowing of the existence of demons , or maybe knowing the prophecy of the prince of dragons (or all together ) are destroyed . 400 years later, events BOF3 with the prophecy of the prince of dragons .
8th - Now, there is only one known Dragon (Ryu, the prince of dragons), but there are members of Dragnier, even giving up his powers, may have children with blood Brood (plus others such as Ryu and Teepo, that are scattered around the world).
9th - It would be nice to make time pass, when Brood was already rebuilt again to face the demons, as in BoF2 (make a BOF4). Remember that in this theory the powers of Myria help keep retained demons (and since she was destroyed, they are on the loose again). It will be a new Ryu in this new world, perhaps destroy the demons once and for all (or put a new phase of history: Brood killers of demons).
That's it folks, this is my theory, is how I see the game world, and how I would like it be.