 While in Hueco Mundo, most hollows can sate their hunger simply by breathing the "reishi"-rich air, and are threatened only by other hollows who have turned to cannibalism, conquest for power and sport, or both.Hueco Mundo is initially portrayed as impossible to access by non-hollows, but techniques for traveling there are eventually revealed, and Hueco Mundo was entered by outsiders, first by protagonist Ichigo Kurosaki and his allies, then later by Quincy conquerors.An enormous white domed palace called in Hueco Mundo, initially ruins, was used by Aizen to garrison his troops.