The mountain itself wasn't anywhere near as deadly as it was in 2nd edition. Saving throws are just soo much easier in 3.x then before, that even using the most powerful poison in the dmg, the characters didn't give a hoot about Clan black death's arrows.
The main way the kobolds gained the "edge" on the pcs, was I had them learn. They learned the pc's tactics, and strategies. They learned what NOT to do.
The first few clans got wiped out fast and gorey, but the farther they went into the mnt. , the harder it got, as the kobolds were ready for them.
My guys min/max a ton, so I had to use alot of magic to counter them as well. But the book says that the dragon provides items of magic to help the kobolds, so i used this to their advantage.
The farther in they went, the less and less they were getting sleep. The kobolds would harrass them constantly. This kept their spells depleted and their fighters fatigued(minuses to hit and such).
Something my kobolds learned fast though, DONT go toe to toe with the pcs... its a slaughterhouse , no matter how many there are.
So, strongest parts, is the sheer number of kobolds lets you make them more and more difficult as they learn the players strats. It kept getting harder and harder and harder until finally the dragon at the end.
Weakest parts, repetition. kobolds.. millions of little buggers.. I rememdied this by adding hit dice to the pets of the kobolds and always made sure to set loose them on the pcs. Bulettes, rust monsters, otylughs, etc..
Had a bitch of a time converting over the Giant Slug too.
Also, the final battle is almost unwinable. You have to tone down the dragon, else its a TPK. Great Wyrm Red > PCs.
The pacing is good, just keep making it harder as they go, like i said.
