Sankhchuda, a mighty daitya underwent terrific tapa and penance and pleased Brahma. Brahma blessed him with a boon of invincibility. Shankhachuda pleased Brahma with his penance, was granted the Vishnu-Kavacha (armour of Vishnu) and he blessed shankhachuda that as long as Vishnu-Kavacha was on his body, no one could slay him. Shankhachuda and Tulsi were soon married. He practiced the laws of dharma religiously but was also prone to commit mistakes and sins for the sake of community. Therefore, after victory over the three worlds, he drove out gods from various celestial kingdoms. To rescue the universe, Shiva challenged Shankhachuda to war. Vishnu appeared in his true form and urged Tulsi to abandon her earthly body and return to his celestial abode. In her anger and grief,she cursed Vishnu to be turned into stone. Vishnu turned into a stone and reside on riverbank Gandaki River. People and devotees will call it a chunk of shaaligrama. Tulsi's mortal remains decayed and became the Gandaki River, while her hair transformed into the sacred Tulsi plant.