Answer
Al-Afdal Shahanshah, the vizier of Egypt, served as the de facto ruler during the reign of Al-Musta'li, the 10th Fatimid caliph. Al-Musta'li was a weak and ineffective ruler, and al-Afdal took advantage of this to consolidate his power and control the affairs of the Fatimid state. Al-Afdal was a skilled military leader and administrator, and he successfully defended Egypt against the Crusaders and other enemies.