This thread is what happens when you let me get on the train to go to work without enough sleep. Let's review, shall we?
Since ancient times in Algo, there has been a cycle where calamities occur every one thousand years. That's because a personification of evil called Dark Force is resurrected every thousand years!
And once every thousand years, when the strength of the seal weakens, the most intense part of the The Profound Darkness' hate-filled spirit is able to break through the portal and come to Algo in physical form.
Oh, the greatest, my one and only ultimate god, Dark Force!
We know that Dark Force is a part of a being with power that we cannot comprehend and that Dark Force itself is beyond human understanding. While that is not enough to consider either of them uncategorically as "gods," it is enough to convince their followers. We also know that Dark Force has ability to lend its power to its minions, as demonstrated by Zio when the evil magician warped the battlefield into "Nightmare."
HOWEVER, Dark Force has always been seen to use a base. In PS1, he used the Governor of Motavia as his host. In PS2, he planted himself within Mother Brain. In PS3, even though Dark Force was bound by Orakio's sword, his host continued to live for over a thousand years. In PS4, he used Kuran, Garubrek Tower, and Seth to spread his power.
In essence, I advance the theory that without a host of some kind, Dark Force is unable to sustain himself in our dimension for long periods of time. We've seen him act without a host only briefly, and that Dark Force was unique as the longest-lived of the Profound Darkness' minions. Most of the time, their lifespans are relatively short, measured in years, not millennium.
Regardless, what we've seen is that Dark Force is an extradimensional being that can be hurt by "light" attacks. This suggests that the Edge and our dimension are yin and yang, with the elements of one unhealthy for the denizens of the opposite. This is further suggested by Le Roof, who states:
As long as you have those Rings of the Stars, you should be able to withstand the largest part of the power of The Darkness.
The Rings act as filters that prevent the Edge from...what? Ripping our puny heroes to their constituent atoms? Possible! In the long run, it's possible that Dark Force needs his hosts in order to prevent the same thing from happening to him. The demons of the Edge likely follow similar rules of some sort, though it's possible Dark Force's power lingers on, considering the evil temples of Dezo in PS2.
So what do you think, guys?