Sometime Lords of Siwa

Bedouin raiders occasionally attack the oasis, raiding the fields in an attempt to capture women, livestock, goods, and supplies. Should the magi arrive while a particularly vicious attack is underway, the elders of Siwa might be willing to enter into an agreement with the wizards, in exchange for the recovery of their kinfolk and a promise of future protection. This desert tribe is different, however. The raiders entered into their own bargain with a sahir, or perhaps even a corrupting and bloodthirsty demon. Saving the people of Siwa means finding them before the tribesmen's patron claims them for its own appetites. The adventure's antagonist need not fight to the death, but instead might become a thorn in the side of the future covenant.