Once a Murmurer (The Murmurers were flowers transformed into soldiers) conjured up by Phobos to do his bidding, Caleb developed a will of his own and broke free of Phobos’ control. He became the leader of the rebel forces who were opposed to Phobos' rule and has quickly gained popularity in Meridian. He is a kind and benevolent young man whose heart was bound to Cornelia’s. Even before he met her, he had dreams about her and has longed to one day meet the girl of his dreams.
After Nerissa's defeat, he decided to return to Meridian, leaving Cornelia disillusioned. By this act he falls into disgrace with the other Guardians, particularly with Irma, who wished to kick him back to Meridian. Eventually, after being in the presence of Elyon for such a long time because he decided to go back to Meridian, he falls in love with her and it is assumed that his affections are requited.
When both Caleb and Cornelia meet again, they have an uneasy time, but after joining hands, they discovered that their feelings have changed, and that even if it didn't work out they will have a special place in their hearts for each other, as dear friends. Some volumes later, after Elyon is taken by the Guardians, he is seen walking by her chamber and thinking about her deeply, admitting to himself he wants her back as soon as possible.
During his time as a herald of Kandrakar he taught Will how to teleport. Soon after that he fell in the hands of Nerissa, who took away his powers to rejuvenate.
In the animated series, Caleb is a human teenager, who started Meridian's resistance movement.
He was first introduced during the series' first episode and initially had a low opinion of the Guardians, seeing the liability created by their inexperience as outweighing the benefits of their powers. However, as Season 1 progressed, and the Guardians learned to use their powers, he changed his mind about them and took full advantage of their abilities in the fight against Phobos.
Personality wise, Caleb is brave and reckless, as well a strong and quick-thinking leader and a good fighter. He tends to be a little arrogant and bad-tempered, with a sarcastic streak. He also fails to understand how girls' minds work (something that gets him in trouble with Cornelia from time to time). Although he puts on a tough and uncaring attitude, Caleb is a loyal friend who sticks to his beliefs no matter what.
Even though he is the only one of the main characters who has no special powers or abilities he is more than able to hold his ground against more powerful opponents with his experience, quick thinking and hand to hand combat skills. Even though his most preferred weapon seems to be a sword he is skilled with the use of other ones too.
In addition to learning to appreciate the Guardians, Caleb soon developed feelings for Cornelia and began a relationship with her. Although it faltered several times, most notably after Elyon took the Meridian throne - leaving him little reason to remain on Earth - they remained together after the point in the comic book where they split up, and were still together by the end of Season 2.
When first introduced, Caleb is an orphan, however part way through Season 1 it is revealed that his father was taken captive rather than killed and that, unaware that he was the rebel leader's father, Phobos had imprisoned him in an underwater mine. With the help of the Guardians, Caleb frees his father, who joins him in command of the rebel army. Caleb's family background is further illuminated to in Season 2 when Nerissa captures Caleb and imprisons him on Mount Thanos. There she reveals that she is his mother, and that she gave birth to him with the intent that he would overthrow Phobos for her.
Nerissa then offers him her power, and command of the army that she intended to raise, in return for his loyalty. Caleb refuses her offer, telling her that he did not overthrow one tyrant from Meridian's throne in order to allow another to take his place, greatly angering her in the process. However, it is to be noted that Nerissa has never actually gotten as far as killing him (even when she had the opportunity). When trapped in the Heart, she tells Elyon: "Caleb is my son. I will not allow Phobos to harm him". In fact, it is revealed in her fantasy universe, that she wished for Julian and Caleb to join her and rule by her side.