I've met a guy named Ishaq. He's some kind of a clairvoyant and he wants to help me. But first I have to provide him with herbs from the river bank that can only be collected at night.
At the Harran University Mufid mentions some loud music being played. After speaking to him, head to the source of the sound. The location is due north of the university, just beyond the canal. The entrance of the place is near the roof of the building, with the entrance being marked with a blue light. The door will open automatically when entering, unlocking a new Safe Zone.
Once inside, head to the back room and speak to Ishaq. Ishaq will state that Crane's "nemesis" sought his guidance but was denied. Ishaq is willing to provide it to Crane, but he needs a special nightshade which grows in the river bank and can only be seen at night. A bed is located in Ishaq's safe zone, so resting until night there is advisable to quickly advance the quest. 6 of the night herbs are required for the quest.
The river bank itself is located to the east of the main road leading out of Old Town. Be wary, as Toads spawn in the same area as the herbs do. The herbs are easy to recognize, as they glow in the dark. After obtaining 6 of them, return to Ishaq and put the herbs in the brazier to complete the quest. Speak to Rashiq again to start the next quest: "The Shadow of the King".