Thomas spent much of his young adult life as a writer, historian, and philosopher, though he derived his income as a printer. He also often served as a lawyer or judge, whenever criminal cases would arise in his village. In 867, he married his girlfriend, Gina, who also often served as a lawyer, when the need arose.
While there had been laws on The Land for centuries before Thomas's time, they had mostly been specific to individual villages. There had also been trials of accused criminals for centuries, but there wasn't an established court system until 899. And while certain people had devoted part of their time to serving as lawyers, over the centuries, it was never a full-time occupation until the court system came into being. However, in 889, Thomas had a book published called Balance of Justice, which he'd spent the last several years writing. (The book was partially inspired by Who Watches the Watch Monogs?, published five centuries earlier.) In it, he explained why he believed that in the near future, it would become necessary for a more complex legal system to be developed, with common laws which would be standardized in every village. The book became fairly popular, particularly with people involved in law enforcement. Thomas also became a popular and well-respected master for anyone seeking to study the law, even though lawyer still wasn't a regular profession. (Most of his students went on to become police.) With the rise of inter-village gangs in 899, talks began in Thomas's home village of Kurok, where delegates from villages around the Land convened to make plans for the establishment of a standardized court system, just as Thomas's book had anticipated ten years earlier. Those talks also led to the establishment of InterVil.
In 904, after the Coming of the Order had been completed the previous year, it was understood that the establishment of the Second Order was imminent. However, the precise form the new government would take was still unclear, in spite of the fact that any number of people had already been campaigning for government positions for the past couple of years, starting even before it was a certainty that there would be a government. Now that it was clear, Thomas was among those people who helped plan out the structure the government would take, including the fact that there should be three branches (executive, legislative, and judicial), to provide "checks and balances," a way of ensuring that no one person or group within the government became too powerful. Later that year, when the first federal elections were held, Thomas was elected to the High Court as Kurok's magistrate. In 905, King Demos Royal appointed Thomas to the position of Chief Magistrate. He was reelected as magistrate in 909, and once again appointed Chief Magistrate in 910.
When the surname law was passed in 904, Thomas and Gina chose the name "Justicar," which was based on an old Terran term, "Justiciar," meaning "man of justice" or "judge." However, it was Thomas's idea to remove the "i" from the word, because he just liked the sound of "Justicar" better.
In 912, Justicar, along with Commissioner Mufasa Gothic of InterVil and Marshal Poss Primus, pardoned members of The Chaos for their alleged plans of rebellion, and specifically pardoned Tiejo Streetrat for his admitted killing (in self-defense) of Macen Illustri and Zeke Sanguine. This led to King Royal sending his own royal guards to arrest Justicar, on 21 Su'yet. Following the end of the Chaos War, on 9 Aut'mo', Demos released Justicar, and he resumed his place on the High Court.