Due to being born only one Wing of the Heart, he is considered to be malformed and monstrous. Because of this, he was scorned by many, and this left him a somewhat bitter young man. His grandfather built him a custom Winglet that would grow with Kalas as a functional substitute for his missing left Wing of the Heart. After his little brother and grandfather, the only lights in his life, were murdered, he set out on a quest for revenge. Kalas's recklessness and desire for vengeance made him vow he would do anything to kill the one who murdered his family, Giacomo. To this end he allied with himself with Melodia, who helped him contract a Guardian Spirit, who would lend him the power to achieve his revenge. In return, Kalas would aid Melodia in resurrecting the evil god, Malpercio. In addition, Melodia promised Kalas beautiful white wings once the god was resurrected. The spirit he contracted eventually rebels against this, but its memory is erased by a spell so it would lend Kalas its power once more.
For these manipulative purposes, Kalas keeps most of this a secret for the first half of the game, and says that he is focused on revenge for his family. Eventually Kalas and Melodia succeed in their goals of releasing the End Magnus. However, when Xelha and his other friends come to try and stop them from fully allowing Malpercio to be brought into the world, Xelha's final prayer before her death by Kalas's hand and his old guardian spirit rejecting him, makes him realize that she was trusting and supported him even though she knew he was lying. With this realization Kalas is capable of escaping his own bitterness, and releases himself from Malpercio's grasp, a feat that a normal mortal could not hope to accomplish even with the help of sacred items. Kalas rejected the power of Malpercio by tearing his left wing, his new wing, out of his back. After the battle with Malpercio, Kalas rejoins the party, this time honestly seeking to undo the wrongs he has done.
Afterwards, the group of heroes spend their time looking for any means to stop Malpercio. Then Larikush, an old colleague of Kalas' grandfather who was a great genius, revealed that Kalas was born not from a human, but from magnus. Because of this, the fortuneteller (earlier in the game) couldn't see his 'magnus', in this context the part of a lifeform which becomes lost when storing it inside a card, making that process impossible. It was an attempt of his grandfather to unravel those cards' secrets and the secrets of life itself. However, Kalas himself was imperfect, which is why he had only one Wing of the Heart. Further experiments finally birthed Fee, Kalas' little brother, who was the perfect lifeform, and referred to as the 'divine child'. Kalas, in a final showdown with Giacomo, the murderer of his Kalas' family, had an epiphany himself. He discovered that he would have died the night of the murders, were it not for his brother who used his powers to save Kalas from the brink of death, and in the process transferred the powers to him, making Kalas the new 'divine child', destined to face off against Malpercio. It is because he has the power of the 'divine child' that Kalas is able to escape from the hold Malpercio has on him.
After the battle had been won, and man returned to the earth, the unleashing of the ocean also made everyone's wings of the heart disappear, in effect also releasing Kalas from his handicap. This, and the relationship with Xelha he ends up having in the end, leaves Kalas with everything he needed and strived for during the game.
