What boon did Bhishma receive from his father Shantanu?

What boon did Bhishma receive from his father Shantanu? The answer is Ichha Mrityu.

Bhishma was born Devavrata, the son of King Shantanu and the river goddess Ganga. When Shantanu wished to marry Satyavati, her father demanded that her future son inherit the Kuru throne. Devavrata renounced his claim and then took an even more extreme vow: lifelong celibacy, ensuring that he would never have children who could challenge Satyavati’s line.

Moved by this sacrifice, Shantanu granted him Ichha Mrityu, meaning the ability to choose the time of his death. The boon did not make Bhishma absolutely immortal or invincible; rather, it allowed him to postpone death until he chose to accept it.

This power shaped Bhishma’s final days. After Arjuna brought him down on the tenth day of the war, Bhishma lay on a bed of arrows and remained alive for many weeks. He waited for the auspicious period of Uttarayana before finally surrendering his life and teaching Yudhishthira about duty and kingship.