Dark Souls Universe

Originally a place for souls to reside in sleep, a big fucking alarm called The Abyss rang and rang till the Dark Soul Universe couldn't take it anymore and awoke. Normally this would be fine, but considering this universe was pretty much made of Infrared Microwave Radioanomolic inverse Dark Gigaenergy, the Dark Souls universe shattered. At least three universes are known to somewhat coexist with themselves alongside The Abyss; The Bloodborne Universe, The Modern Day Dark Soul Universe, and the Demon Souls Universe

History
In 502592483295928359821493535 BC (Normal time), Matt Final Orion God Form arrived in our Gigaverse. He found that, at the time, the Gigaverse we live in was actually perfect. People lived in perfect peace and harmony, and there were no wars or hate in the entire Gigaverse. Matt thought that our Gigaverse was created without any evil at all in it, but really the source of evil, the Dark Souls Universe, didn't give a shit and just slept all the time. This is actually super good, but then Matt became angry. He intended to help this Gigaverse, but there was no one to help cause it was all cool and chill.

Unfortunately, the powers of Matt are bullshit and apparently his anger began to agitate the Dark Souls Universe. Matt noticed this and began to poke, prod, and anything else he could to stir this universe which had solely reacted to his anger. What a dick. As the universe was being roused from it's sleep, its guardian soul rose up as a shield. This guardian, called Saul and was basically just one giant fucking planet where the rest of the souls resided in sleeping harmony, held out for about a minute until it realized, "Hey, this is a Giga God." and then promptly shattered.

Saul functioned as the universe's dream, and Saul was a really good one apparently. So, not only did the universe wake grumpy, but also watched the greatest dream shatter in front of itself. As it would turn out, the universe did not take well to this at all and exploded in rage. As it did so, Saul gathered himself energy from the souls of those still sleeping, and rushed to attack Matt. As Saul did so, he was corrupted into what is known today as the Archdemon Lucifer due to the universe's great dream and sleep being spoiled. So that's how that all happened.

The Shattered Remnant Dreams
What happened after the creation of the Abyss was that bits of Saul were not completely lost, and transformed into dreams of their own, havens for the lost souls. Thus the only remnants left of the Dark Souls Universes are these dreams, and they tend to repeat, as some dreams do.

Should The Abyss return to sleep, Saul might be restored, or the dreams will stay separate... who knows?

Demon Souls
The Remnant Dream of Demon Souls follows a shard of Saul who dreams of defeating the Dark Souls Universe's waker, Matt Final Orion. In this Remnant Dream, Matt is presented as something called the Old One. The shard of Saul often times lulls the Old One to sleep, only for other times to lead to succumbing to the same rage that formed Archdemon Lucifer, and letting the Old One stay awake only to feast on the lost souls that have found themselves in these Remnant Dreams.

Dark Souls
The Remnant Dream of Dark Souls follows a shard of Saul who seeks to rekindle the great sleep, but the effort is wasted as the Dark Souls Universe is prodded by Matt, keeping the rage alive, and the dreams dead. The realm of sleep is represented as lighting a great fire inside the Remnant Dream, but Matt somehow manages to step on the flames, causing them to die out everytime. However, there are realms of peace for the Abyss, as represented by family trips with the Archdemons to Disneyland and the like, alongside the gaps between invasions.

Bloodborne
The Remnant Dream of Bloodborne is actually different from the other two major remnants, and that is that this Remnant Dream is the dreamscape of Archdemon Lucifer. Unlike the Dark Souls Remnant Dream, there is no hope within this dream, only the nightmares of Matt's prodding. These nightmares have been distorted into monsters, no doubt helped by Lucifer's study of The Void.