Vajrasattva

Vajrasattva is the esoteric Buddhist name of the bodhisattva Samantabhadra. In esoteric Vajrayana Buddhism, many Buddhist figures assume different identities to signify their esoteric, as opposed to exoteric, form. Vajrasattva is an important figure in two esoteric Buddhist sutras, the Mahavairocana Sutra and the Vajrasekhara Sutra. In both sutras, Vajrasattva plays the role of the student, who learns the Dharma from Mahavairocana Buddha, and is taught the esoteric rituals to help actualize the Dharma.
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[Other] The third Dhyani-Buddha of Nepal to whom the final part of the night is dedicated. His color is white and his attributes are a bolt of lightning (vajra) and a clock. 

Vajrasattva (Sanskrit) [from vajra diamond + sattva essence, reality] Diamond-heart, diamond-essence; a title given to mahatmas of the highest grade, or to bodhisattvas whose whole personality as a living essence is merged in their compound sixth and seventh principles (atman-buddhi). Vajra here expresses the spiritual adamantine quality of the inner natures of these glorious beings. Vajrasattva is a manifestation of the heart of vajradhara, the First Logos or adi-buddha; hence vajrasattva is "the second logos of creation, from whom emanate the seven (in the exoteric blind the five) Dhyani Buddhas, called the Anupadaka, 'the parentless,' " (SD 1:571). Dorjesempa is the Tibetan equivalent.
Vajrasattva is often used for celestial beings, entities belonging to the hierarchy of light or compassion. The vajrasattva quality is likewise one which can be possessed in less degree by any human being, depending upon his degree of advancement.