Rha is an extremely weak, ancient star which is notable for the fact that it is almost entirely encased within the artificial planet Korod. At one point, Rha was called "the Crucible", the name bestowed upon it by the salarian explorers who discovered it during an expedition on Korod in 1982 CE, and the star system is still called the Crucible system, but the skurid who populate Korod's interior apparently refer to the star as Rha, and so that is the name recognized upon Citadel-approved starcharts. The star's advanced state of decay has been blamed upon Korod's construction; the mysterious beings who created the planet placed at its core hundreds of thousands of pipes made of korodium, a mysterious alloy capable of absorbing extreme heat, and these pipes have, over the millenia (and possibly eons) since, drained away much of the star's mass.
The Crucible system itself is nearly dead; the surrounding planets are deserted husks, incapable of supporting even the simplest life-forms. In recent years, this has resulted in the system becoming a base of operations for the terrorist group Purple Spawn.