Afterwards mantras were used extra to guard the spiritual lifetime of the chanter, and sections on mantras started to be included in some Mahayana sutras such as the White Lotus Sutra, along with the Lankavatara Sutra. The scope of safety also altered in this time. From the Sutra of Golden https://vashikarantotke34310.blogocial.com/about-mantra-68469816