Dark Sun Adventure Idea 3

Players should not read any further. Dungeon Master eyes only!

Setup: The first Yuan-Ti created an artifact that can change large groups of humans into Yuan-Ti. The artifact was split among the various Yuan-Ti tribes and quickly lost during some internal Yuan-Ti conflicts and they have been searching for it ever since. Some humanoid Yuan-Ti have hired scholars and adventurers to locate and secure the artifact. Years of work have been successful and only a single piece of the artifact remains lost.
Until now. An adventering group recovered the last piece and was in the process of handing it over to the Yuan-Ti, when they discovered the devices nefarious purpose. Instead of returning it, they fled toward another city-state.
The Yuan-Ti, however, are not foolish and were using a silver piece, enhanced with psionics to track them. They knew instantly that the group had betrayed them and set out to get the artifact from them. They abushed the group and a battle ensued. During the chaos, a member of the group named Fedil, took the last piece and ran into the desert.

Plot: As the party is walking around, outside a city, the see Fedil in the distance. He collapses. When the party investigates, as they hopefully will, they find the staff piece, still clutched in his hands. Fedil will tell the group what is going on and begs them for help. The Yuan-Ti are following Fedil's tracks and will seek to get the artifact back by any means. The party must out maneuver the Yuan-Ti and find a way to destroy the artifact they hold.

For added interest, Fedil could be carrying the psionically enhanced silver piece. The Yuan-Ti can easily track them and even guess where they are headed.

Or the artifact piece Fedil was carrying was a fake. The group has to decide if they will find the real piece, or maybe it's ready too late.