A King's Ransom

As mentioned, the Tablet of Iron that protected the sarcophagus and spirit of King Kush was removed by Emir Musa. This left the king vulnerable and the sarcophagus (with the corpse and ghost of the king) was taken by the Malik. This theft ensures the submission and service of the Prince and his spectral soldiers, who now serve as guardians to prevent outsiders from using the Marble Palace as a gateway into the Magic Realm. Though reluctant to stop his father's potential rescuers, the prince is bound to do so and tries to turn them away (by force if need be).

Once the prince sees how powerful the characters are, he turns against the Malik and asks them to rescue his father. If he thinks he can get the upper hand over them, such as by demanding a hostage to ensure cooperation, he does so. If he thinks the magi are extremely powerful, though, he is more humble in requesting assistance. If the characters strike a fair and honorable deal with the prince and do manage to liberate the king, then they may be able to call upon the prince and his spectral army for assistance in other matters.

If the Tablet of Iron was the primary motivation for the expedition, then the characters have travelled to this point to return the tablet and speak to Prince Keshan. He explains the situation, and tries to negotiate for assistance. He takes a humble tone, but is insistent and resorts to coercion if the characters refuse.

If the characters had another motive for traveling to the City of Brass, and encounter the ghosts unexpectedly, the prince reacts in a more confrontational manner. The characters are not permitted to pass through unless they first strike a bargain. Since the magical gateway requires travelers to first pass through these tombs in order to later find the Brass Horseman that leads to the City of Brass, this becomes an unavoidable plot point.