Up until now, one of the flat miḥrāb-s in the Mosque of Ibn Ṭūlūn in Cairo keeps its mystery. Of its damaged decoration, in all likelihood dating back to the Ṭūlūnid period, only the central motif remains, consisting of a circled star hanging from a chain. This article examines the original significance of this miḥrāb. First, the foundation stele of the mosque provides an epigraphic context characterized by the predominance of an eschatological discourse. From there, I explore several hypotheses by engaging with textual and archaeological traditions relating to the themes of the star and the chain. The star could represent the " pearly star " evoking the infinite light of paradise in the Qur'ān. The chain may in turn refer to the chain of the Banū Isrā'īl, a symbol of the absolute justice that God supposedly granted to Prophet David. Considering Ibn Tūlūn's attempts to appear as a just ruler, one might see in this miḥrāb an evocation of the Last Judgment, which Ibn Ṭūlūn could have used to highlight his own justice.