Brainstorming...
themind said:
I've been running an Eberron game ... <snip>
1. Going down into Khyber to retrieve a Khyber Dragonshard needed.
The Dragonshard is being held by a mad-priest of a cult of Khyber. They have taken the shard to their stronghold deep underground to their hold: a giant stalactite. This giant stalactite hangs over a bottomless pit with strange heat and magical emanations drifting up. The cult believes the pit leads straight to Khyber itself (and maybe they are right!) and pray/sacrifice to the Dragon below in exotic ceremonies that culminate in the victims getting thrown into the pit.
The priest is collecting great Shards. He is experimenting with the magic of the pit (or the essence of Khyber seeping up) to turn Shards into powerful artifacts.
He is turning them into great reservoirs of fiendish power to fuel massive new Warforged creations. You then place a few of these creations as encounters in the "reverse tower" dungeon of the stalagmite to shake things up. Warforged powered by small “enriched" Khybershards embedded in them. (Just take the Warforged and add the Draconic and Fiendish templates, doctor the appearance to taste, add levels to balance the ECL if necessary, stir, and boom: Erie new abomination from below).
The party takes on the stalactite-dungeon like working from a tower down, maybe a good fight on a great bridge spanning the chasm to the Stalactite (gives you a chance to show the dungeon off and create wonder/horror/adventure with the group at the prospect of going in).
The group goes in and begins the dungeon crawl. Fiends and abominations are probably useful as these relate to an Eberron "Underdark", but don't over do it or they will lose their wonder/exotic factor. Throw in some cultists, regular warforged, and don't forget some of your personal favorite monsters (like CE said) to liven things up. Take some hints of your story arc and add an encounter (like an ambasador from the Lords of Dust) or somesuch to foreshadow the future.
The party should run into the new "Warforged" by the middle, give the players that "what the hell is that?" moment. Now they now something foul is a-foot and needs to be fixed before it gets out of control. Of course, the mad priest is at the bottom. A final fight on a great balcony overlooking the pit would be epic and memorable. Give a few henchman bull rush to really scare the @#$% out of the players (look mom, I could die with all my hit points!).
Of course, this is pulp-fiction, so when the great Dragonshard is retrieved from it's mantle, the lights dim and a rumbling starts. Turns out the Shard they needed was already powering something: the base. Now the magic is ruined! The stalactite starts to fall apart as the magic that powered it is gone. The abomination of the dungeon and its contents are returning to Khyber and taking the players with them if they don’t move fast (starting with the balcony!). The characters better have magic ready (Yea, right, not after fighting their way to the dungeon’s boss) or they are going to have to race back up through the stalactite and across the bridge. Hope they looted on the way, they won't have time now
Throw in lots a flavor text as they run up stairs that are crumbling and falling into the pit behind them, dodging stones falling down, a jump check (not hard, just for flavor) to get to the bridge as the Stalactite is already pulling away, etc. Ham it up. This is Eberron.
Some ideas, hope they help.
Good luck!