Phobos was the false ruler of Meridian during the years when his sister and rightful monarch, Elyon, lived in Heatherfield on Earth. His age is currently unknown, it is only known that he is older than Elyon.
When we first encounter Phobos he is searching for his sister in the hopes of getting her magical powers for himself, and in killing her this would make him the only person of royal blood and make his rule complete.
Elyon was taken to Earth 12 years ago and Phobos has been ruling in her stead but he has depleted the world of Meridian. Only thinking of himself all the citizens of Meridian are poor and live like slaves.
After finding Elyon and having his trusted minion Cedric “brainwash” her into thinking that the guardians are the villains, he belies that his victory is in sight. What he does not know is that Elyon just in time have learned the truth about him. He is then put in jail in Kandrakar, in the Tower of Mist. This however is not the end of Phobos.
He begins to poison the mind of his warden, Endarno, and builds his way up in Kandrakar. He beings to plant the seed of doubt that the current Oracle is not fit for his job. He manages to have the Oracle removed and takes on the job him self still in the form of Endarno. The guardians with the help of Yan Lin see past this charade and after revealing him for who he really is. He realizes that this battle is lost and he jumps over the edge for Kandakar into the never ending void beneath.