Isaturin is a minor character in The Defenders of Shannara trilogy. He was an Elven Druid specifically chosen by Aphenglow Elessedil before her death to succeed her as Ard Rhys of the fourth Druid Order.
Isaturin was considered an even better magic wielder than Aphenglow, with powerful abilities such as being able to teleport himself short distances. He also served as a Druid ambassador, representing Aphenglow and the Druid Order across the Four Lands.
Before Isaturin became Ard Rhys of the Druid Order, the sorcerer Arcannen disguised himself as Isaturin and visited the Federation's Minister of Security, Fashton Caeil. In disguise, Arcannen killed the Minister with the Stiehl and left, leaving the Stiehl at the scene of the crime to pin the blame on the Druids and their weapons of magic in order to foment discord between the Druids and the Federation. However, despite many in the populace believing that the murder was carried out by the Druids, the Federation's Prime Minister was not fooled, and he visited Aphenglow privately to exchange information. They confirmed that Isaturin was in Paranor at the time of the murder and that the murderer was most likely Arcannen.
Shortly afterward, Aphenglow traveled out of Paranor in her personal airship with Paxon Leah, the newly recruited Blade of the Ard Rhys, as well as with her young assistant Sebec and several of the Trolls serving as Druid Guards. When they reached the Streleheim Plains, Aphenglow announced that Sebec was the traitor within the Druid Order who had been passing information and artifacts of magic to Arcannen, including the Stiehl. Sebec had even attempted to steal the crimson Elfstones. For these crimes, the Ard Rhys had the guards execute him.
After Paxon has been serving as the Blade of the Ard Rhys for five years, time and age caught up to Aphenglow and she prepared to die. Paxon and Isaturin traveled with her to the Hadeshorn, where they watched the shade of Allanon bear her away into the lake. Paxon barely had time to mourn when Isaturin, as the new Ard Rhys, called on him and the Druid Avelene to undertake a quest to investigate the possible use of the wishsong in the Southland.
Paxon and Avelene were harried in their quest by Arcannen, and Avelene ended up trapped in a magical container created by the sorcerer. Paxon was forced to suspend his pursuit of Reyn Frosch, the boy who possessed the wishsong, and take Avelene back to Paranor, where Isaturin and other Druids managed to free her from the prison. Avelene was physically unharmed but left deeply traumatized.
Later, after witnessing the massacre of the Federation's entire Red Slash unit and the killing of Avelene at the hands of Arcannen, Paxon was left emotionally bereft and sickened by all he had seen in his time as the Ard Rhys's Blade. He requested to Isaturin that he be allowed some time away from Paranor, which Isaturin granted. After living with Leofur Rai for some time in Wayford and committing to be her life partner, Paxon returned to Paranor with her and resumed his duties.
As part of his duties, Paxon accompanied a Druid peace delegation on an ill-fated mission to meet and negotiate with the Federation in Arishaig, serving as part of the Druid Guard. When the Federation peace delegation was attacked and killed by a Sleath, Isaturin and the warrior Druid Miriya used their magic to defend the Druids, but the Sleath was able to penetrate their shields easily. In all the commotion Paxon was unable to get close enough to the beast to confront it with the Sword of Leah. It was only through the attempts of the Druid seer Karlin Ryl to communicate with the monster that it ended up vanishing, breaking into pieces and seemingly passing through Karlin's body as it disappeared.
Paxon was almost immediately convinced that Arcannen was responsible for the Sleath and its slaughter, but the fact that the monster did not kill any Druids and the way the creature responded to Karlin's magic and passed through her as it vanished convinced the Commander of the Federation's Ministerial Watch, Fero Darz, that the Druids were the murderers. He attempted to stop the Druid delegation from leaving, but their magic prevented him from doing so.
After the Druids escaped Arishaig in a stolen airship, the ship crashed in a storm south of the Battlemound Lowlands. As the surviving Druids continued their escape on foot over the flatlands, Miriya confided to Paxon that Karlin, her life partner, was behaving strangely, avoiding Miriya and refusing to speak. Paxon attempted to speak to Karlin himself but also got nowhere.
While pursuing the Druids on foot, Fero Darz stumbled into a Druid-created mist and was captured by Paxon. Paxon stripped the Commander of his weapons and kept him close, hoping to convince him that the Druids were not responsible for the slaughter of the Federation peace delegation. Although unwilling to admit to it completely when Paxon confronted him, Darz did express that he had doubts.
Paxon led Darz and the surviving members of the Druid company towards the Lower Anar, hoping to get the party to Culhaven where they would be able to find transport back to Paranor. When they were almost to the Anar, Karlin fell into a trance, caught in the thrall of a vision. Although she struggled to speak, she managed to proclaim that the airship had crashed and that everyone had died. Paxon initially thought Karlin was referring to their own crash, but she clarified and said that the entire company of soldiers aboard the large Federation cruiser that had been pursuing them had been wiped out in a crash. On the heels of this stunning announcement, Karlin turned to Paxon and begged for his help.
As the party made their way to the Anar, a large wall of mist and an impassable stand of odd-looking, moving trees appeared. Wary of the danger ahead but realizing the need to find transport as soon as possible, the party pressed on through the trees.
While passing through the trees, the old Druid Consloe slipped and made contact with one of them, awakening the trees and causing them to lash out with countless grasping tentacles and roots. Consloe was captured almost immediately and dragged below ground by the roots. Paxon, Isaturin, and Miriya were quickly surrounded on all sides by the trees' attacks which separate them from Karlin, Fero Darz, and the remainder of the Druid Guard.
Suddenly Karlin screamed and the Sleath reappeared out of her body. It rushed at the trees, doing enough damage that the trees eventually had to direct all their attention to subduing the Sleath, and the party were able to make a break for it. The trees managed to kill the monster, but the party was safely away by the time they'd done so.
Karlin, who had collapsed after the Sleath left her body, ended up dying quickly, leaving Miriya distraught. Strangely, Isaturin said nothing in condolences to Miriya, and when pressed to do so by Paxon, he outright refused. Miriya vowed to avenge Karlin's death by finding and killing Arcannen, and Paxon agreed to help her.
Unwilling to face the prospect of more of the monstrous trees, the party changed course and headed into the Wolfsktaag Mountains to get to the Anar. Deep in the mountains, a dragon emerged and killed the remainder of the Druid Guard as the party attempted to cross a ledge connecting one cliff edge to another in order to get down the other side of the mountain. Paxon drew the Sword of Leah and the sudden light from the blade blinded the monster, causing it to lose its footing. It slammed into Paxon and Miriya and took them with it as it fell off the ledge. Left alone with Fero Darz, Isaturin grabbed the Commander and threw him off the ledge before making his way off the mountain by himself.
Paxon and Miriya's fall was broken by a tree growing on the side of the cliff, and Paxon witnessed Fero Darz falling to his death. Paxon woke Miriya and slowly they climbed up back to the ledge, making their way across and down the mountain. They walked all night and morning and were found at the edge of the forest by a kind Dwarf named Trond Ulkend, who took them back to his village where they were given time to recover and a small airship to take them back to Paranor. They inquirde after Isaturin, but no news of the Ard Rhys had reached the Dwarves.
On their way back Paxon realized how strange it was that Fero Darz fell off the mountain after the threat of the dragon had passed, and how no one had seen Isaturin despite him being the only one to not fall off the ledge. He also called to mind Isaturin's callousness after Karlin's death, and how odd it was that the Ard Rhys had seemed content to let Paxon take the lead in bring the Druids home to Paranor safely.
Paxon voiced his suspicions to Miriya, adding that whoever was controlling the Sleath had to have been present at the time of its attacks, and that Arcannen had once disguised himself as Isaturin in an attempt to bring blame down the Druids when he had killed the Federation Minister of Security Against Magic, Fashton Caeil. Paxon and Miriya realized that Isaturin must have been captured or killed, that Arcannen must have been posing as Isaturin since at least the time of the Sleath's first appearance, and that the sorcerer was probably headed to Paranor posing as the Ard Rhys.
Paxon and Miriya arrived at Paranor to find it surrounded by Federation warships, looking for answers to the deaths of their peace delegation. They land on the outskirts of Paranor and were immediately pursued by Federation troops. Miriya managed to find one of the secret underground passages into Paranor and they made it inside the Druid's Keep safely. Inside, they ran into Oost Mondara, who told them that Isaturin had returned, that Paxon's sister Chrysallin had gone missing the day the Federation's peace delegation was murdered, and that Leofur had left Paranor with the manager of the stables in search of Chrysallin.
Paxon was distraught at Chrysallin and Leofur's disappearances but forced himself to focus on the task at hand. He and Miriya explained their suspicions to Oost and the three headed to the chamber where the Druids' most important artifacts of magic were kept, which was where Oost was headed in search of Isaturin before he ran into Paxon and Miriya. There in the chambers they found the body of Keratrix, the Ard Rhys's personal assistant. His neck had been broken and it was clear that parts of the chamber had been raided.
Paxon, Miriya and Oost raced to where the Druid airships were kept to find Arcannen, still in the form of Isaturin, boarding one of the ships. Upon seeing Paxon and Miriya, the false Ard Rhys halted their advance with a wall of magic fire and fled in the ship. Paxon and Miriya followed closely after him, with Miriya using her magic to keep track of the sorcerer. The pair tracked Arcannen all the way to the ruins of Kern, where Arcannen set down his airship and made his stand.
Paxon and Miriya hunted for Arcannen within the ruins, barely avoiding traps and always several steps behind the sorcerer as they proceeded cautiously. They realized that continuing on without changing tactics would cause them to eventually lose Arcannen, so they decided that one of them should rush into battle against the sorcerer and the other one should try to come around the sorcerer from behind while he was engaged.
Miriya rushed in and attacks the sorcerer, but Arcannen put up a magical wall which separated Paxon from Miriya and delayed him just long enough that he was unable to help her. Arcannen killed Miriya and threw her into a pit, and as he fled Paxon chased after him up a flight of stairs. He injured himself when the stairway collapsed, and Arcannen hit him with his magic while he was stunned and defenseless. Paxon got up and attacked Arcannen with the Sword of Leah, but because of his injuries and the fact that he was still weak from his journey out of the Southland and into the Anar, he was unable to call on much magic from the sword and Arcannen deflected his attack easily.
Paxon was saved when Miriya, who had not been killed and was just badly injured, came up from behind Arcannen and stabbed the sorcerer through the chest with a steel rod. As the sorcerer died, Paxon cut off his head. The two recovered the Druid artifacts stolen by Arcannen and headed back to Paranor, where a Druid delegation presented the Federation warships with Arcannen's head and Paxon and Miriya's explanation of events. Although they were not completely convinced, the Federation forces were appeased enough by the explanation and the gift of Arcannen's head to stand down and leave Paranor.
Although Isaturin was a capable Druid, when Aphenglow died he was in the unenviable position of having his performance as Ard Rhys constantly compared to her own immensely long and successful career. His time as Ard Rhys was short-lived, for he was killed by Arcannen after just a few years as Ard Rhys. After Paxon and Miriya killed Arcannen, Miriya's name was one of the ones floated as a possible successor to Isaturin.