Decades ago, a young Xudarian scientist, Tomar-Re, was approached by the Guardians of the Universe to wield the Power Ring of the Green Lantern Corps. Tomar-Re went on to have a long and distinguished career as a Green Lantern. To better perform his duties, Tomar-Re developed the Zathon Ray Communicator which could warn of disasters on other worlds in his sector. Tomar-Re also kept a watchful eye for his neighbouring Green Lantern of Space Sector 2814, Hal Jordan. He warned his fellow ring wielder of any perils, including a violent cosmic storm that once struck Xudar. 
The Xudarians have taken a benevolent interest in the universe they have one of the most peaceful histories in the cosmos. In the 1950's, a Xudarian science expedition came to the planet Earth, but ere attacked by the Weaponers of Qward. Apart from Green Lantern representatives the Xudarians have not been seen much in the vicinity of Earth since then.
Tomar-Re eventually retired from active duty with the Green Lantern Corps, joining the prestigious Honor Guard. Even then, he would still prove the faith his fellow ring wielders had in him, leading a contingent of the Corps against Krona and Nekron. Tomar-Re’s successor was Dalor of Timron. Dalor was mistakenly believed dead during the so-called Crisis on Infinite Earths, and Tomar-Re still wielded the Power Ring. With the Central Power Battery offline, Tomar-Re brought a group Corps to Oa to assist the Guardians. Tomar-Re was later killed in the Anti-Matter Universe by the Earth villain Goldface.