Darius', Ruyan's and Faeana's souls being joined together by the Soul Bind curse.
In Forever Kingdom, the Soul Bind is a curse placed on Darius, Ruyan and Faeana which causes them to share the same life force. Thus, if a member of Darius' party is attacked, then they all endure damage. Consequently, healing one character also heals the other two, as well.
Generally, a 'Soul' gauge measures the overall life force of the party, which is displayed at the bottom-left corner of the screen. When damage is taken by any of the three player-characters, the gauge decreases. If the gauge is completely depleted, then the entire party perishes simultaneously. While proving to be somewhat frustrating, the game features an option which allows characters who share one life gauge.
The Soul Bind does not affect Felkin and Saris, who temporarily join the party at a few points in the story.
Story[]
Faeana and Ruyan about to experience the Soul Bind.
Darius, Ruyan and Faeana are in the midst of a search for the Forsaken Village; they need to find the village before sunset. Suddenly, Faeana hears a rather strange sound, which Darius and Ruyan cannot hear. Interpreting the sound as a call for help, she rushes off, leaving Darius and Ruyan to pursue her.
The three friends come across a young girl in the stranglehold of Darsul; close by is his sidekick, Drumhort. Faeana tells Darius to let the girl go, but is held back by Drumhort's sword. Darius and Ruyan ask what Darsul and Drumhort are planning to do with the girl. Drumhort responds by single-handedly swinging his sword at Ruyan, knocking Ruyan's spear off. Darius comes to Ruyan's rescue and tries to hold back Drumhort's sword with both his hands, but finds himself too weak to hold out against Drumhort.
In response to the affair, Darsul casts the Soul Bind on Darius and his friends. He calls it "a simple lesson to teach (them) not to interfere with other people's affairs."
Drumhort implies that the Soul Bind was meant to be cast on Solca as well, saying to Darsul, "(y)ou missed her...". During the time the Soul Bind was cast, Solca managed to run away to safety. Believing that she had run for the Dandelion Field, Darsul and Drumhort leave to pursue her.
While Darius and Faeana contemplate what just happened to them, Ruyan explains he has heard about this curse, and tells them about the effects of the Soul Bind. Ruyan thinks that Darsul and Drumhort are "more than just kidnappers," and Darius and his companions set out to catch them and find out more about them.
The Soul Bind is implied to be dispelled as soon as the party defeat and release the souls of Solca and Karmyla within the confines of the Truth Crystal.