Johan became a Squire Dragon initially because he believed following Orin and recording his exploits in the form of epic poetry would allow Johan to make a name for himself in the literary community. He took the Trials out of necessity (which in those early years were much easier than in later generations) and became a Slayer Dragon at the age of 25.
At the age of 32, Orin made the unlikely choice to name Johan the next Pendragon, believeing that as a youth, he may well become the next Emily. Unlike Emily, Johan was not groomed to become Pendragon from the age of 9; thus he was less than fit for the job.
Johan's service as Pendragon would last only 5 years, but he would forever be remembered as the worst Pendragon in history. He was lax in his personal training, and made little effort to champion the ideals of the Slayer Dragons. He seldom left Arindell, and fought in few battles. The other Slayer Dragons of the time were quick to point out how he drew the sword less than once each year.
Thoroughly unfit for the position and feeling crushed by the weight of responsibility, Johan attempted to flee Arindell, but was very quickly hunted down and brought to trial. To escape punishment, he decided to stand down as Pendragon and pass the sword to Ace Barnam, a fellow Slayer Dragon who had been anointed shortly before Johan.
Disgraced and outcast, and overcome by guilt, Johan left Arindell. He was rumored to be in exile, but Ace routinely and publicly stated that this was not true.
Johan likely returned to Sindall and lived in isolation, possibly under an assumed name. He was only 37.
Nothing is known about how long he lived after leaving Arindell, though it is believed he could not have lived long. Every Pendragon before him passed on the sword on the day of death.