The dakini Singhamukha (Goddess with a Lioness' Head) was spoken of by the Biessed One in the tantras, in order to guard against harm caused by those who use sorcery against the teachings and other beings.
Vajrapani doesn't many newcomers to Buddhism, look very Buddhist at all. He is a Bodhisattva who represents the energy of the enlightened mind, and his mantra also symbolizes that quality.