The T'Syriél were towering, powerfully built humanoids who originated from the planet known as Shiva IV. Organized as the Twelve Tribes of T'Syriél, these beings were long-standing adversaries of the Human Calian Confederacy. Their extensive wars shaped a formidable and respected warrior culture. However, in the year 2 ABY, the Concordat of Peace marked the end of these conflicts. Despite this, many dissatisfied T'Syriél were exploited as soldiers during the Imperial General Bentilais san Sk'ar's attempt to seize control of their world.
During the time of the Galactic Civil War, T'Syriél society was structured around the Twelve Tribes of T'Syriél, each governed by a Demarch. Nevertheless, a considerable number of T'Syriél existed outside this structure, forming bandit groups in the planet's desolate regions. Their history of relentless warfare had instilled a strong warrior ethos, although its influence had begun to wane by 3 ABY.
For countless generations, the T'Syriél engaged in constant battles on Shiva IV against the Human inhabitants of the Calian Confederacy. This relentless warfare transformed them into formidable warriors. This era of conflict concluded in 2 ABY when Demarch Kéral Longknife and Calian Warlord Aron Peacebringer signed the Concordat of Peace, forging an alliance between their peoples. However, this treaty did not resolve all issues for the T'Syriél. In the subsequent months, numerous outcast T'Syriél abandoned their traditional values, losing the spirit that had defined them as powerful warriors.
In 3 ABY, many of these T'Syriél outcasts were recruited by Imperial General Bentilais san Sk'ar, a Kaleesh tasked with conquering Shiva IV for the Empire. Sk'ar strategically employed both T'Syriél and Humans in his forces, intending to sow discord between the Twelve Tribes and the Confederacy by creating the illusion of betrayal. Some T'Syriél fought wearing modified stormtrooper armor during Sk'ar's attempted takeover. Ultimately, Peacebringer, Longknife, and members of the Rebel Alliance joined forces to thwart Sk'ar's scheme.
The T'Syriél made their debut appearance in Star Wars (1977) 53, a comic written by Chris Claremont and published in 1981. The majority of the artwork featured in Star Wars issues 53 and 54 was initially created for a different project: Marvel Comics' John Carter, Warlord of Mars series, which was canceled in 1979. To utilize roughly 30 pages of fully-penciled artwork, Marvel commissioned artist Carmine Infantino to adapt the existing pages for Star Wars, transforming the native Martians into the T'Syriél.