Vajrasattva is a tantric archetype deity. Like Manjushri, Avalokitesvara, Tara, and the other celestial Bodhisattvas, he is a Buddha who persists in a Bodhisattva form to help beings on the path. Sattva means "spiritual hero or heroine," and vajra (diamond or thunderbolt) is associated with power and maleness.

Vajrasattva is the subject of many hymns and verses. He is supplicated in the special yoga of repentance that employs his special, well-known hundred-syllable mantra. He is represented seated in the dhyanasana, holding a vajra before his heart in his right hand and a bell in his left hand, which rests akimbo on the left thigh. The vajra and the bell are symbolic of compassion and wisdom, male and female, magic body and clear light, respectively, depending on the level of reference of the symbolism.

This description by Nitin Kumar, Executive Editor, Exotic India.

References:

Rhie, Marylin M., and Robert A.F. Thurma. Wisdom and Compassion: The Sacred Art of Tibet: London, Thames and Hudson, 1996.