"Kongōrikishi (金剛力士) or Niō (仁王) are two wrath-filled and muscular guardians of the Buddha, standing today at the entrance of many Buddhist temples all across Asia including China, Japan and Korea in the form of frightening wrestler-like statues.
They are manifestations of the Bodhisattva Vajrapāṇi protector deity and the oldest and most powerful of the Mahayana pantheon. According to Japanese tradition, they travelled with the historical Buddha to protect him and there are references to this in the Theravada Scriptures as well as the Ambatta Sutta. Within the generally pacifist tradition of Buddhism, stories of Niō guardians like Kongōrikishi justified the use of physical force to protect cherished values and beliefs against evil. Nio-Vajrapani is also seen as a manifestation of Mahasthamaprapta or the Bodhisattva of Power that flanks Amida in the Pure Land Tradition and as Vajrasattva, the Dharmapala of the Tibetan tradition...
...Kongōrikishi are a possible case of the transmission of the image of the Greek hero Heracles to East Asia along the Silk Road. Heracles was used in Greco-Buddhist art to represent Vajrapani, the protector of the Buddha (See also Image), and his representation
was then used in China and Japan to depict the protector gods of Buddhist temples. This transmission is part of the wider Greco-Buddhist syncretic phenomenon, where Buddhism interacted with the Hellenistic culture of Central Asia from the 4th century BC to the 4th century AD.