Om - the sound of the universe itself. The imperishable sound is the seed of all that exists. The past, the present, the future. - all are but the unfolding of OM. And whatever transcends the three realms of time. That indeed is the flowering of OM.
Padmasambhava also known as Guru Rinpoche was the key in establishing Buddhism to Tibet by subduing hostile forces to Dharma. Not by destroying those forces but subduing and making them into protectors of Buddhism.