Zuben Elgenubi at the Stormspire wants you to obtain a Farahlite Core.
Now that we've got a good baseline product, we're going to need something of higher quality. Certainly the farahlite we've gathered so far is nice, but I know there's better out there.
We'll have to get a sample directly from Cragskaar, the patriarch of the Farahlon giants! You should be able to find it among the other giants in the Netherstone area. It's got huge pieces of farahlite jutting from its back and that's exactly what we need. Fell the giant and collect a farahlite core from it.