- The Rad Zone is a region of Cybertron in the Marvel Comics portion of the Generation One continuity family.
The Rad Zone is where Grimlock stored a trio of stolen Decepticon ships, including the Graviton. Apparently even the Decepticons don't go there. Why? Who knows? The answer probably involves how badass Grimlock is. (One might hazard a guess that it is a region of high radiation, possibly the result of some incident during the war, similar to the Acid Wastes)
Whether or not this zone wants to tell you about the Transformers remains to be seen.