This is a timeline from an Athas where an event diverging from the normal flow of history has serious consequences for Tyr.
Year of the Priest’s Defiance, 190th King Age - so-called " Free Year 1". King Kalak is assassinated by the heroes of Tyr. Tithian, a high templar under Kalak becomes King.
Free Year 2. King Hamanu orders an attack on Tyr, but his armies are repelled by the Crimson Legion led by Rikus.
Free Year 3. By unknown means, Sadira becomes the only Sun Wizard on Athas, thereby achieving great power.
Free Year 4. King Tithian begins the search for an artifact that can turn him into a Sorcerer King.
Free Year 9. The River of Time branches off. At the cusp of finding the artifact that can turn him into a Sorcerer King, Tithian is captured by Agis, Rikus and Sadira, and returned to Tyr to face trial for his crimes. The Council of Advisors puts Tithian to trial, and Tithian is sentenced to death for treason and murder. Tithian is publicly executed. Subsequently, the monarchy is abolished and the the Council of Advisors selects a chancellor to lead. Sadira, due to her magical powers and connection with the council factions led by Agis and Rikus is made chancellor.
Free Year 10. Unbeknownst to the the Council of Advisors, after the war with Urik, King Tithian had an agreement with the Sorcerer Monarchs of the Tyr region brokered by the Dragon to keep Tyr safe from attack in exchange for Tithian assisting the Dragon in finding the artifact that could purportedly turn Tithian into a Sorcerer King. With Tithian dead and the artifact still unfound, the agreement is now null and void.
Free Year 11. In the Tablelands beyond the Tyr region, there is a small city ruled by a Sorcerer King styled Magnate Baeron of Senn. Senn is a dying city, the arable farmlands and grazing lands collapsing every year. Told by the Dragon that he could have Tyr if he could take it by force, Magnate Baeron spent all of Free Year 10 preparing a great migratory army, taking every able bodied person with him on a march to Tyr with the slogan “victory or death”. The city was abandoned to the elderly and every templar left with their leader.
Great battles ensued against Tyrian armies once near Tyr. The penultimate battle was fought outside the city walls and in the city streets. Sadira personally entered the fray against Magnate Baeron. While almost equalling Magnate Baeron in sorcery, Sadira had little defence against his psionic attacks. To save her own life, Sadira teleports away to safety, leaving the citizens of Tyr to their fate.
Despite great resistance, the free people of Tyr were defeated. From former slave, to freeman, to Tyrian nobleman, every Tyrian citizen was made a slave and forced to serve the Sennish invaders. Thereafter, Baeron was styled the Iron Magnate of Tyr. Iron flowed from the mines and the Iron Magnate, although a lesser Sorcerer Monarch in terms of personal power, became the wealthiest. During the reign of Kalak, slaves outnumbered citizens two-to-one, at that time considered an extremely high ratio of slaves. Under the Iron Magnate, slaves outnumber citizens four-to-one, as the entire “free city” had been enslaved by the conquerors.
Tyr is now known as the Shackled City, and the Free Year calendar has been abolished.