[2] The son of a Christian woman,[3] nothing is known of his early life until he appears in the chronicles in 1013, when the reigning caliph, al-Hakim bi-Amr Allah (r. 996–1021) chose to name him as his heir-apparent.

Shortly after, during the Eid al-Adha festivities, Ibn Ilyas substituted for the caliph, and a formal proclamation as heir-apparent, with the traditional title of walī ʿahd al-muslimīn, followed in September or October of the same year.

[4] This appointment was a major break with Fatimid tradition, where the oldest surviving son had always been the designated heir; it even threatened to provoke a religious schism, as father-to-son succession was a fundamental tenet of Isma'ili dogma.

[10] Moreover, al-Hakim specified that while Ibn Ilyas would become caliph (khalīfa) after his death, the position of Imam of the Isma'ili faith would pass to another distant relative, Abu Hashim al-Abbas, a great-grandson of al-Mahdi, thus separating the civilian and spiritual aspects of his office.

[11][12] For the Isma'ili faithful, the latter was the more important, but Abd al-Rahim was evidently the more favoured and prominent of the two, as evidenced by the different treatment meted out to the two men after al-Hakim's death.

[20] In the meantime, Sitt al-Mulk, who sponsored the succession of al-Hakim's son Ali, soon secured her position as the de facto head of the new regime, and on 26 March, during the Eid al-Adha festival, the death of al-Hakim and the succession of Ali, with the regnal name al-Zahir li-i'zaz Din Allah (r. 1021–1036), were announced.