According to many Hindu religious scriptures, there is a mention about immortality. Those who receive this immortality never die. The same has been mentioned in Rigveda as well. There is a famous ancient story about immortality. As per the story, after being cursed by Maharshi Durvasa when Indra Dev along with other Gods had become too weak, the demons had attacked and defeated them.
After being defeated by the demons, all the Gods went up to Lord Vishnu and narrated the incident before him.