"Message for Ellhrah" is a mission in Geneforge
The mission can be started only after completing Clear Watchhill.
Once that is done, speak to Khobar if he needs any other work done. He asks you to deliver a message to Ellhrah in his Keep.
Since Watchhill is already cleared out for the most part (you may encounter some stragglers, but for the most part it will be devoid of hostles), just pass through it.
Once you reach Ellhrah's Keep, talk to him and deliver the letter. Ellhrah then reads the letter and explains the mission was mostly just a pretext to get you to talk with him.