Wikipedia
( Sanskrit: " Vajra in [his] hand") is one of the earliest-appearing bodhisattvas in Mahayana Buddhism. He is the protector and guide of Gautama Buddha and rose to symbolize the Buddha's power. The Golden Light Sutra titles him "great general of the yakshas".
Vajrapāni also called Vajrasattva, in Mahayana Buddhism, is extensively represented in Buddhist iconography as one of the earliest three protective deities or bodhisattvas surrounding the Buddha. Each of them symbolizes one of the Buddha's virtues: Mañjuśrī manifests all the Buddhas' wisdom, Avalokiteśvara manifests all the Buddhas' immense compassion, and Vajrapāni protects Buddha and manifests all the Buddhas' power as well as the power of all five tathāgatas ( Buddhahood of the rank of Buddha).
Vajrapāni is one of the earliest Dharmapalas and the only Buddhist deity to be mentioned in the Pāli Canon as well as worshiped in the Shaolin Monastery, in Tibetan Buddhism and in Pure Land Buddhism (where he is known as Mahasthamaprapta and forms a triad with Amitābha and Avalokiteśvara). Manifestations of Vajrapāni can also be found in many Buddhist temples in Japan as Dharma protectors called Nio. Vajrapāni is also associated with Acala, who is venerated as Fudo-Myō in Japan, where he is serenaded as the holder of the vajra.