Rann is the home planet of the Rannians and their champion Adam Strange. They are a race devoted to scientific development and are generally displayed to have poor relations with the more military minded Thanagar. In the Silver Age stories one of the most common threats on the planet during the adventures of Adam and Alanna was a wild beast called a Tigrabar. This animal showed up on numerous occasions.
Mystery in Space
The planet of Rann was featured most often in the tales of Adam Strange and Alanna in the silver age, of which the majority of the appearances appeared in Mystery in Space. Adam would habitually wait on Earth for the appearances of the zeta beam after which he would be transported to Rann. At various times the planet was described, but this was more often for the purpose of plot and not as related to any actual firm understanding of the planet (save for the capital city of Ranagar.) Like most silver age stories, the stories of Adam Strange were serialized, meaning that there was little continuity between issues, and this held true with the portrayal of the planet as well. Rannians were shown to be fairly similar to people from Earth, including such similar activities as going to the beach. The natives of Rann are even referred to as humans fairly often in the text, though in the story the gravity on the planet is slightly weaker which aids in Adam being more physically robust than they are.
At the climax of Planet Heist, Sh'ri Valkyr used the Omega-Beam to transport Rann into the same orbit as Thanagar. The gravitational stress of having two planets in one orbit caused Thanagar to move and burn up in the sun. The damage to the planet was seen as an act of war by the Thanagarians, leading to the Rann-Thanagar War and eventually the Holy War.
The end of Rann
In the events of the Holy War between Rann and Thanagar, Rann was besieged by Thanagarians forces who swore the destruction of Rann, the lethal army of Lady Styx and Synnar's Inquisitors. With no hope to survive the imminent destruction, Adam Strange developed a risky plan to stop the Demiurge and save the Rannians but the ultimate price they will have to pay was the destruction of their homeworld. Using the Weird as a nuclear bomb, they destroyed Synnar and in the last second teleported themselves and all the Rannians to Prince Gavyn's Throneworld.
Now, Rann is merely a dead world and the Rannians have migrated to Throneworld aka New Rann.
After joining L.E.G.I.O.N to battle Starro the conqueror Adam Strange commented on how though most of the Rannians had found a new home on New Rann, a large majority were still living on refuge ships. Vril Dox, now with no base of operation decided that he could solve both his base problem and the Rann problem. Using the largest Zeta beam available L.E.G.I.O.N transported the whole of planet Rann to the Vega System, now in the orbit of the former planat Tamaran, and started teraforming. Within a matter of weeks the planet Rann was once more habitable, with many Rannians now returning to it. But not only would the revival of Rann give a home to those Rannians who could not find a home on New Rann, but also to the Tamaranians who's new kingdom exists on Rann's southern continent as was proposed in a new treaty between Rann, Thanagar and Tamaran created by Vril Dox. Rann is also the new headquarters of the intergalactic space force L.E.G.I.O.N.