Hulagu took Baghdad and killed the last Abbasid caliph in 1258, chroniclers gave seven different deaths, and a surviving kinsman was made caliph in Cairo

In 1258 the Mongol prince Hulagu took Baghdad, and the Abbasid caliph al-Musta'sim died on or about 20 February. Nassima Neggaz's 2020 study in the Journal of the Royal Asiatic Society lists the accounts of his death. Rashid al-Din tells a starvation story, then says he was killed at the village of Waqf with his eldest son and some eunuchs. Joinville has him held in an iron cage without food. Wassaf says he was rolled in a carpet and trampled. Ibn al-Fuwati says he was put in a sack and trampled, so his blood was not shed. Qazvini says the Mongols broke his head. The Georgian Chronicle gives the final blow to Ilge Noyan. Ibn al-Ibri says he was executed with his middle son and six eunuchs. Marco Polo's book has Hulagu shut him in his own treasure tower to starve^†. Neggaz judges trampling most likely, because Mongol custom avoided shedding royal blood. The title survived. Abbasid kinsmen scattered, and in 1261 and 1262 the Mamluk sultan Baybars invested two survivors as caliph in Cairo. The first, al-Mustansir, was killed in 1261 on an expedition to retake Baghdad^†. The second, al-Hakim, reigned until 1302. His descendants held the caliphate in Cairo under the Mamluks until the Ottomans conquered Egypt in 1517.