Actually, according to japanese ps 2, Dark Force existed on Earth. It was what caused the Earthmen to destroy their world. I'll quote the japanese:
First is the quote of Dark Force before you fight him, next is the Earthman leader story:
Voice- Ha ha ha ha ha ha!! Welcome to the ultimate trap, the Pandora's box! Inside it contains the force of darkness that you call the Dark False. This is our little gift to your world from us!
Yushisu- What is going on? Who are these people?
Captain- Welcome aboard Noah, Algolians.
Yushisu Who are you people?
Captain- Now let's not be too hostile, you must be thinking we are your enemy, are you not? <question 1>
Reply Yes to question 1- Well that's sad to hear. Indeed, we must say you are our hated enemy too after you have destroyed our Mother Brain.
<point A> Yushisu-So it is you who created Mother Brian, is it not? Who are you people?
Captain-We are not Algorians. We come from a far away planet called Earth. It is one of the planets that supported life. We created a large civilization there, which flourished for millions of years (note the word millions...clearly, Bill Gates isn't behind Mother Brain after all). We are the last bloodline of the inhabitants of planet Earth.
Yushisu-The last bloodline?
Captain-Yes, our home no longer exists. Do you wish to know why? <question 2>
Reply Yes to Question 2- By looking at it now, we must regret that we were fools. We knew the evil force, Dark Farusu, existed in our minds, but was unable to suppress it. We soon began to grow fond of controlling the natural world through scientific means. We only recognized we were killing ourselves when the planet began to crumble before our very own eyes. The survivors, which you see now, barely made it to this ship and escaped. We wondered hopelessly through the universe searching for another home. Then we found Algol, your star system. We gloated over your peaceful lives, your lives without the presence of evil. That was when we vowed to ourselves to take over your star system no matter what it took. Soon, we were able to destroy your planet of Parma. Certainly you are no fools to oppose us with such a powerful force, are you not? You shall now die for us and for our future.
Reply No to question 2- Well, certainly it make no sense for you to learn why we ended up like this, since you are going to die anyway is that not right? <question 3>
Reply Yes question 3- We are simply taking what we lost from you, there is nothing else to it. We lost Mother Brain, but with our remaining technology, we will be able to rule Algol with ease. You are the only ones opposing us. Algol shall be ours if you are not present. All of our opposition shall die, including you.
Reply No to question 3- Well, if you wish to hear our desperate struggle, we shall certainly tell you. (goto Reply yes to Question 1)
Reply No to question 1- Yes, we are merely your creators that helped you modernize with Mother Brain's help. (Go to point A)
So as you see, Dark Force in Ps 2 is the same type of Dark Force in PS 3. Dark Force in PS 3 existed in the mind of Rulakir and fed off of him keeping alive.
Dark Force with Lashiec was the same way.
It seems Dark Force feeds of negative energy of individuals.
Apparently the Earthmen also seemed to think the people living in Algo were without evil(Dark Force corruption) So they wanted Algo?
Besides, 3/4 endings of Ps 3 are the same.
Sean - Neo palm joins them and they'll work together in 1000 years when Dark Force rearises.
Crys - 3rd planet from the sun
Aron - Earth and London contact (3rd planet from the SUN)
Adan - 3rd planet from the sun again
Adan - Neo Palm eradicated
Aron - Neo Palm eradicated
Crys - Neo Palm is never seen and could be considered gone
Sean - Neo palm works with them in 1000 years
So we have a 3 out of 4 endings on a 3rd planet from the sun (Could be Earth in all 3).. We also have 3 out of 4 with no neo palm..
SO Dark Force according to 1, 2, 3 can exist outside 1000 year periods..
Hm..