Ragnara Exclusion Zone

The system variously known as the Forbidden World, The Blighted Start, and Ragnara's Star, is off limits. The Mercantile Consortium and the Thimblebottom Empire agree on few things, but this is one of them. Both organizations, and most space fairing people, have rules that ban visiting the system.
The entity called Ragnara was an occasional blight in the Eubuleus galaxy. At regular intervals millennia long, the Ragnara comet would appear and smash into a healthy planet. This god-like being would then thoroughly corrupt the life of that world into horrifying forms. Such being were hardy and impossible to kill. They were violent against all life not native to this world. As a result, such planets were forever ruined for the rest of the galaxy.
On its most recent appearance, a joint effort of many space-fairing peoples managed to seal it on the world it struck. For concern that the seal would be broken, or that some of the corruption would be carried off world, no one is allowed to go there.
Space-born golem ships patrol the system. They warn off incoming ships. Anyone who does not heed their warning will be marked for destruction.