The Jungle of Yrae was a lush tropical forest srrounding a swampy lake found in the southeastern region of Idryllia, just north and inside the eastern arc of the Bleeding Sun Mountains.
It long served as a hunting grounds and agricultural support region for Mardok, until the Age of Knowledge. During that time, the Beastmen were pushed back into the jungle, but Aergoth's army could not meet them in the jungle terrain effectively, and the Arcane Society's clockworks were poorly suited for the uneven terrain as well.
The Society sent a covert force to enter the Underworld through the Beastmen's mining tunnels, and breached into an Ether Pocket (unknown to them, the prison of Baelgar) causing the lake to drain into the pocket, and rendering the region into the barren desert of Dry Lake.
The few scholars who have managed to study the Beastmen have found that Yrae is a name used by the Primordials for the region, its origins unknown.