Tidarion was a lowborn mage of Planasene blood. His father was a Legate in the Imperial Army who taught him swordplay and tactics before his magical abilities manifested themselves. Tidarion's magical talent eventually drew the attention of Archon Almadrius himself, who took him as an apprentice. The magisters believed that magic was a favor of the Old Gods rather than an accident of birth, and refused to acknowledge the mage underclass of elves and newly liberated foreigners. As such, the outraged Magisterium refused to even acknowledge Tidarion as a possible candidate. Almadrius had many rivals, and though he survived many assassination attempts, none of his Altus apprentices did. When the magisters finally had Almadrius assassinated, Tidarion remained his only heir.
When the magisters refused to recognize him as Archon, Tidarion took the throne by force, marching the legions into the Magisterium and slaughtering all those who wouldn't swear fealty to him. The Seven Temples declared Tidarion a usurper, and the legion was divided. Some generals supported the temples while some supported the Archon. The mages of the Laetan class overwhelmingly supported Tidarion. Mages were fighting each other for the first time since the fall of Arlathan. The Imperium plunged into a civil war.
Tidarion converted his predecessor's great summer palace near the Eyes of Nocen into a garrison for his troops fighting the insurrections all across the Imperium. To protect his palace, Almadrius had stationed one hundred soldiers on permanent guard, making them swear blood oaths to serve only the Archon himself. Tidarion made use of them in the civil war, and though the centurions eventually fell in battle, their oaths held and their bodies rose again to take their posts. The palace and centurions had both disappeared by the time Tidarion's successor came to claim them.
Tidarion was notable for fighting with a blade like a commoner, while casting spells like only an Archon could. He eventually died sword in hand on the battlefield, having carved and burned a brutal path across Tevinter. Tidarion had named no heir and as such the civil war did not end with his death. It lasted for twenty more years, until -620 Ancient, when Archon Parthenius, former high priest of Dumat, finally admitted the Laetans to the temples and gave them three seats in the Magisterium.
- Tidarion used Tacitus Valerius as Imperator of the Legion for the entirety of his reign. It was rumored that his maul had broken so many priests of the Old Gods that their blood had fused it with their spite so that no one should ever stand before the weapon that had felled them.