Well we can consider Rulakir/Dark Force to be a Dark Force/Lashiec relationship.
Dark Force gave Lashiec eternal life, Rulakir has been alive for 1000 years feeding Dark Force negative emotions.
If we use the english Ps 3 script..
- The ultimate evil dwells on a floating city in the
barren waste lands of the dome named Terminus.
- A word of ultimate power has been lost for ages. This
name can empower the weapons of legend.
- To discover the lost name, you must first find all
five weapons of ancient legend.
- The ancient heroes used the legendary weapons. These
are Orakio's Sword, Miun's Claw, Siren's Shot, Laya's
Bow, and Lune's Slicer.
and then..
- Hatred keeps Rulakir alive after 1,000 years!
- We wanted Siren and Lune to start another war, but we
needed Rhys to bring Satellite back. And that's
exactly what that old fool did!
- Centuries ago, Laya locked the passageways between the
domed worlds of our ship, Alisa III. But your father
and grandfather opened them up again, enabling us to
spread evil once more!
Guards:
- Dark Force brings your doom, fools!
- You fools have done everything we wanted!
Rulakir:
My heart went black 1,000 years ago, when my family died in
the Laya-Orakio war. Dark Force owns my soul and he shall
own yours!
Rulakir:
You have freed me; destroy Dark Force!
Narrator:
Rulakir is dead; finally he is at peace.
(The party finds Dark Force in a chest in Lashute’s
dungeon.)
Dark Force:
I am Dark Force, master of Death! Your sorrow, anger, and
pain are my strength! Observe my might and despair of life,
fools! I will greatly enjoy your painful deaths!
So what we have here is Dark Force feeding off of Rulakir as he is imprisoned. We have the sages of Lashute instigating everything and causing the Alisa III to destroy a ship, go to black hole, etc.
Then we have that the only way to stop evil is to get the legendary word of power. Unfortunately you have to GET 5 legendary weapons to get it.
When you pull out Orakio's sword, Dark Force finally breaks free and flees back to Lashute to feed off of Rulakir.
Also, Lashute doesn't turn evil until the sword is removed. When Dark Force is freed, Lashute becomes evil.
So if we look at it, we have Dark Force feeding off of Rulakir to keep him alive. We then have to free the great evil before we can destroy it with weapons charged by the word of power.
Orakio and Laya didn't have the word of power and so the only way to stop Dark Force was to imprison him.
It comes down to Dark Force can live off of people's emotions just like he fed off of Lashiec, Earthmen and Zio.
It also comes down to Rulakir is immortal by Dark Force. When Dark Force is free, Dark Force moves back to Lashute and turns the city evil and removes Rulakir's immortality. Rulakir dies and you free him but Dark Force is still alive.
I geuss it's a Rulakir = host for Dark Force to survive while imprisoned and then Dark Force can exist on his own.