What version are you running? 4e or 3e?
The Taranesti were an elf culture that lived in Ycengled (in the northern area of what is now Shahalesti). They were a bit more comfortable with darkness and demon summoning and the like, and the Shahalesti have a big 'light' schtick. Plus Shaaladel was hoping to get his hands on the young dragon Trilla, daughter of Syana. Trilla was integral to the creation of the Torch of the Burning Sky, and Shaaladel wanted his own.
Cue a little war, a little genocide, a bunch of torture, and the near-annihilation of the Taranesti. The party ends up in Ycengled in adventure seven, trying to chase down Rhuarc, the half-Taranesti assassin who killed Coaltongue and took the Torch.