Plot help needed (4e, dark sun)

[Char_Aznable]

Hello,

My players are 9th level and have been steadily traveling west to Tyr to confirm all of the rumors they've heard about the city's new predicament. They have passed Shazlim, (after beating back the hordes of the Far Realm at an abandoned psion's tower) and are quickly approaching the Silver Springs Oasis.

The next adventure will have the group facing up against an invasion Argosy from Urik. Their target is not the Silver Springs Oasis, but rather, the forts on the road to Tyr. The twist is that the general leading the assault along the roads doesn't appear to have many troops. The reason is that he is an accomplished Summoner, who has turned to summoning demons and elementals to do the dirtiest of work.

I have a basic idea of a plot, I've drawn out the argosy and statted out most of the npcs the group will be facing. I need a twist that will make the Argosy a recognizable hurdle for the group to overcome.

Any ideas?

 

[joeye]

plots and places can be neutral or relate to any game or system in our pc.

 

[Char_Aznable]

plots and places can be neutral or relate to any game or system in our pc.

I figured that by giving the most information I could, someone could point out something that I missed. I have an idea, I have places in mind ( the Argosy, the Silver Springs Oasis, and another Oasis used for more demon summoning) but the idea is missing something that feels almost fundamental. Maybe I should just start from scratch and save the Argosy map for another day?

 

[TheClone]

The first diea that psrings to my mind is to make it a defiling device. Is the summoning somehow arcane? Considering demons I think yes and some sorcerers in Dark Sun enslave elementals, so that is a "maybe". Maybe it has some more defiling devices attached to it and leaves a trail of defiled terrain behind. You can use the defiling terrain presented in the last chapter of the creature catalog (don't know the level, but that should be adoptable). Using arcane magic inside the Argosy or next to it could also some soem strange effects. Maybe this defiling idea as a theme to the Argosy works as the twist you need.

If something else comes to my mind, I'll be back.