How During the Abbasid dynasty what event marked the permanent end of the caliphate?

The permanent end of the caliphate during the Abbasid dynasty is marked by the Mongol invasion of Baghdad in 1258. The Mongols, led by Hulagu Khan, sacked the city, resulting in the death of the last Abbasid caliph, Al-Musta'sim, and the destruction of the Abbasid political and cultural center. This event effectively dismantled the institution of the caliphate in Baghdad, leading to a significant decline in Abbasid power and influence. After this, the caliphate continued in a limited capacity under various successors, but it never regained its former prominence.