Short answers, pulled from the story.
Frostating was one of four ancient regional assemblies, called lagting, in medieval Norway. It served as the judicial and legislative body for Trøndelag, Nordmøre, and Hålogaland, with its seat at Tinghaugen in what is now Frosta Municipality. It predates the Viking Age and is arguably Norway's oldest court.
The Frostating held its sessions at Tinghaugen, a site close to the medieval church at Logtun, in what is now Frosta Municipality in Norway. The name Tinghaugen comes from the Old Norse words for assembly (þing) and hill (haugr). A standing stone, the Frostatinget bautasten, marks the site today.
In 1274, King Magnus the Lawmender promulgated the landslov, a unified national law code for the Kingdom of Norway, with the consent of all four lagting. The new law replaced the older Frostathing Law and significantly reduced the Frostating's legislative power, centralising authority under the crown. The landslov remained in force until 1660.
The Frostating seal shows King Magnus the Lawmender seated on his throne, handing the new law to the lawman at the Frostating. Three rows of representatives stand to the king's left, and two bowmen appear at the bottom, each aiming at an animal in a tree. The original seal is preserved in the Diplomatarium Norvegicum on a document dated the 1st of June 1453.
The landslov of 1274 remained in force until 1660, when Frederik III of Denmark-Norway declared absolute monarchy. This change was then codified in the King Act of 1665, which served as the constitutional foundation of the Union of Denmark-Norway until 1814.
Before the Norwegian landslov of 1274, only two comparable unified national law codes existed: the Liber Augustalis, promulgated in 1231 in the Kingdom of Sicily by Frederick II, Holy Roman Emperor, and the Fuero Real, compiled during the reign of Alfonso X of Castile. A unified code for an entire country was exceptional for its time.