Mahakala

Mahakala is a Dharmapala ("protector of dharma") in Vajrayana Buddhism (Tibetan Buddhism and Japanese Shingon Buddhism).In Japanese Buddhism, Mahakala (Jpn: Daikoku), belongs to the fourth hierarchy of deities (tenbu).
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[Hindu] "Great Time". One of the destructive aspects of Shiva in Vedic Hinduism, time being seen as the destroyer of all things.

Mahakala (Sanskrit) [from maha great + kala time] Great time; a name of Siva as the destroyer, and of Vishnu as the preserver.

This is the wrathful form of Avalokiteshvara, the Bodhisattva of Compassion. He protects from dangers and bad influences that might hinder a monk's approach to enlightenment. Mahakala is seen as the protector of the Dalai Lamas.