Blue Demon of the Desert

The creature known as 'The Blue Demon of the Desert' is an ancient behir, a blue multi-legged reptilian monster which spits lightning. It has laired in the Hinjaz mountain ranges for several centuries, periodically venturing out to attack passing caravans. Survivors of attacks have only gasped out stories of flashing lightning, relentless blue avalanches and storms of legs and teeth. No caravan which was attacked has ever managed to fight it off, and there have never been enough survivors, or in good enough condition, to track it to its lair.
The periods between its attacks have grown longer and longer, but every time the locals hope that whatever the monster is, it has died of old age, there has been another attack to dash their hopes.
The Demon's lair is dug out of the rock of the mountain range, with sandy parts turned glassy with its breath weapon. The looping coils of the tunnels curve back on one another, with sudden vertical drops or ascents which pursuers cannot follow before it has circled back around and struck them from behind. The deepest part of the lair has been padded with dragged-away rugs, wall-hangings, bolts of silk and the like to make itself a nest.
Part of the excavation has broken through into a long-buried saurian temple, swallowed by an earth subsidence eons ago. Within the temple awaits the mummified saurian mage-pharaoh Hsssthak, waiting for long eons in stasis for the foretold day when he could pass on to his lizardfolk descendants the key to their resurgence to supremacy.