Handpainted Thangka of Vajrapani.
Vajrapāṇi (from Sanskrit vajra, "thunderbolt" or "diamond" and pāṇi, lit. "in the hand") is one of the earliest bodhisattvas of Mahayana Buddhism. He is the protector and guide of the Buddha, and rose to symbolize the Buddha's power. Vajrapani was used extensively in Buddhist iconography as one of the three protective deities surrounding the Buddha. Each of them symbolizes one of the Buddha's virtues: Manjusri (the manifestation of all the Buddhas' wisdom), Avalokitesvara (the manifestation of all the Buddhas' compassion) and Vajrapani (the manifestation of all the Buddhas' power).
On the popular level, Vajrapani, Holder of the Thunderbolt Scepter (symbolizing the power of compassion), is the Bodhisattva who represents the power of all the Buddhas, just as Avalokitesvara represents their great compassion, Manjushri their wisdom, and Tara their miraculous deeds. For the yogi, Vajrapani is a means of accomplishing fierce determination and symbolizes unrelenting effectiveness in the conquest of negativity.
The Mantra oṃ vajrapāṇi hūṃ pad is associated with Vajrapani. His Seed Syllable is hūṃ.