Yad-Raghesh, the Effondré Rajah was an Overlord from the Âge des Démons who is presumed “dead.”

Yad-Raghesh, the Effondré Rajah was the first Overlord defeated by the Dragons during the Âge des Démons. Since his death his body has sunken into an area now known as The Vale of the Effondré Rajah in the Lumière de Siberys in Argonnessen, where it pollutes the land. His corruption has only spread as the centuries have passed. A host of diables now spawn from the corruption of his corpse, which plague the Dragons of the Lumière de Siberys to this day.

Yad-Raghesh's chosen form was that of a colossal two-headed tigerlike-fiend.

As with all Maîtres Démoniaques, Yad-Raghesh had no true form, and could assume any shape of his choosing between  Fine and Colossal size.

His exact domains and area of influence are unknown, though may include some form of corruption or blight given the state of the land around his corpse.How exactly does a Rajah like Yad-Raghesh die?

He doesn’t. That’s the point of Yad-Raghesh’s tale; his apparent death appears to be a shocking, one-of-a-kind victory, but it is later discovered that rather than dying, he has simply spread his spirit across the Vale, transforming it into a pit of corruption that spawns fiends and slowly expands. If Yad-Raghesh was truly “dead”, the blight on the land would pass; it’s the presence of his spirit that keeps it alive and growing.

Now, to be clear: An Overlord can be temporarily killed the standard way – by reducing his hit points below zero. It’s simply that this doesn’t last for long; he returns within a day. In the case of Yad-Raghesh, he didn’t return and thus appeared to have been truly defeated. This turned out to be a false hope. By transforming himself in this way, he at least partially escaped the binding of the Flamme d'Argent; he can’t return to his original form, but his power is continuing to spread while the other Maîtres Démoniaques are held in check.

As for what he represents, I would say corruption. He gave up his physical existence to BECOME the corruption he embodied.

A host of diables spawns from the blighted area around his corpse. Given his apparently dead state, it is unknown if he has access to the abilities shared by other Maîtres Démoniaques to perceive his servants, ruins from the Âge des Démons, or a specific area when his name or title is spoken aloud.

Yad-Raghesh embodies the concept of corruption, and that his “death” appeared to be a false hope and may have been meant to allow his blight to set into the immediate area of his corpse. He also mentioned that this may have allowed Yad-Raghesh to avoid being bound by the Flamme d'Argent in the same way as the other Maîtres Démoniaques.