- "The kingdom of Liberl, in which we live, sits on the western half of the Zemuria continent, and abounds with nature and deep-rooted traditions."
- —Scherazard Harvey on Liberl
Ten years before the start of Trails in the Sky, Liberl was the target of a large-scale invasion by the Erebonian Empire, also known as the Hundred Days War. Peace has been returned by Queen Alicia II, until a coup d'etat by Alan Richard.
During the events of Trails in the Sky, Estelle and Joshua Bright are traveling throughout every region of Liberl to try to upgrade their bracer ranks from junior to senior bracers. While finishing countless missions all over Liberl, they come to discover Richard's coup d'etat attempt and try to stop him. Richard manages to open the gate to the Aureole Ruins and unseals one of the seals of Aureole, but eventually come to realise that he was tricked and manipulated by Ouroboros.
In Trails In the Sky SC, the secret society named Ouroboros ramped up their operations in Liberl.
The Liberl Kingdom has control over five main cities: Rolent, Bose, Ruan, Zeiss and Grancel. Liberl is on the western half of the Zemuria Continent. It is flanked by the Erebonian Empire on the north and the Republic of Calvard on the east.
A diverse country in which culture is bursting, Liberl has both industrial and rural landmarks. It is rich in sepith and thus has superior technological resources.
Each region of Liberl has its own specialty and trade. Rolent specialises in the supplying of timber and mining, Bose relies on tradings with the Erebonian Empire, Ruan focuses on tourism (before, it was fishing), Zeiss specialises in orbments and mechanics, and Grancel is the political capital.
Liberl maintains a small army of infantry, patrol ships and airships. Despite Liberl's advantage in orbment technology, the country is neither a match for Erebonia nor Calvard in numbers. Instead, Liberl's military relies on seizing the technological advantage to defeat their foes. In the opening days of the Hundred Days War, Erebonia's invasion force into Liberl was three times as big as Liberl's military at the time and included orbal-powered tanks. Thanks to the development of the high-speed military airship, Liberl mounted a counterattack at the Haken Gate, severing the supply lines of Erebonia's invasion force as they suffer massive losses trying to capture Grancel.
With two superpowers sharing its borders, Liberl's infantry constantly train to fight scenarios where they're outnumbered. The country invests on its fleet of airships, divided into attack, scout, and transport ships. While the number of available airships isn't mentioned, General Morgan briefly mentioned in the run-up to Operation: Dragon Capture that the operation would involve 12 airships, around two-fifths of the current Liberl air fleet. The flagship of the air fleet is the Arseille.
Leiston Fortress is the heart of the Liberl military's command and control. Situated at the southern shore of Lake Valleria, this well-guarded facility houses the bulk of the kingdom's active and reserve units. Its strategic location on the lake shore allows it to send reinforcements to any of the five regions, including Grancel. The fortress is also responsible for guarding invading navies from breaking through Ruan by the river and threatening the capital, just like how the Erebonian Navy attempted such a feat during the war.
Grancel Castle is guarded by an elite squad of knights under the command of Captain Julia Schwarz. While small in number compared to the Royal Army, countless battles have proven that they can fight as well, if not better than the average soldier. They also operate orbal artillery batteries for defense against ground threats like orbal tanks.
- In an interview with Toshiro Kondo, it was discovered that Liberl Kindom's real world counterpart and inspiration was Thailand.