“Khadein, city of magic. Ever since Gharnef named himself ruler of this mecca for the magically inclined, the sands surrounding it had run red. Many knights had tried to oust Gharnef, but what defense did they have against the mages the fiend had bent to his purpose? One by one the heroes fell to blades unseen and fires within their armor; and it was not long at all before Khadein's wickedness outstripped its wisdom.”
The following part of this article contains strategy; therefore, it is subjective, and may not work for everyone.
Be aware that Gharnef is invulnerable to attacks in this chapter. Just ignore/avoid him; he will leave of his own accord after Turn 6. Alternatively, block off the eastern bridge with your highest-resistance unit (Caeda is a good option for her Resistance, and her Speed will make her avoid Gharnef's attacks), and augment them with a Barrier Staff or Pure Water to keep him at bay and heal the unit whenever he/she takes too much damage. Also, it is highly recommended that you bring as many magical classes and flying units as possible, as they are the only ground units that are not affected by desert terrain and flying units can fly over water and defeat other enemies while Gharnef is elsewhere. They are also the best candidates for defense from Gharnef.