Robin

“A distinct maṇḍala initiation ceremony was introduced to China in the middle of the seventh century. It brings together a rich set of existing ritual instructions for individual deities, typically organized around images, to create a ceremony that initiates the candidate into a common ritual tradition (a “secret dharma storehouse”). This maṇḍala initiation continues to occupy a central place in medieval Esoteric Buddhist ritual, though both the rituals for individual deities and the initiation itself have undergone profound changes.”
― Koichi Shinohara, Spells, Images, and Mandalas: Tracing the Evolution of Esoteric Buddhist Rituals