Try the Wretched Tide, Swarm of Dretches.
A swarm of demons sure fits the theme for the Well of Demons better than a young green dragon.
Swarm of Dretches certainly got my attention!
A quick search revealed an official 4E conversion document:
http://www.wizards.com/dnd/files/Yuanti_4E.pdf
Seeing that it is for 7th level, this may just slot in perfectly with my Heroic Tier script:
http://www.enworld.org/forum/4e-dis...ampaign-renamed-need-1st-level-adventure.html
Back to Thunderspire: while there is room for the Huge swarm in the center of the Well of Demons, leaving that area would involve squeezing. Anyone know if that woul'd negatively impact the encounter?
Try the Wretched Tide, Swarm of Dretches.
A swarm of demons sure fits the theme for the Well of Demons better than a young green dragon.
The key is to get a mobile foe so that he makes the PCs engage all the traps in the area. Personally I think you should also get one that slows/immobilizes and flings people around so that he can make some good use of that nasty rolling ball.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.