Mutik Tsenpo, younger son of Tri Songdetsen, ruled Tibet from 804 until 815. His reign, characterized by the full adoption of Buddhism in Tibet, was followed by Tri Relpachen (known also as Tri Tsukdetsen) from 815 until 838. Relpachen continued to support the development of Buddhism, though later histories suggest his rule was extreme and overly punitive. Relpachen was assassinated by his own brother Udum Tsenpo (also known as Langdarma), who then took power. While later histories portray Udum Tsenpo as an enemy of Buddhism, it is not clear that, other than limiting financial support, he actively persecuted Buddhism. Udum Tsenpo ruled from 842; a lively tradition of historical legend retells how he was assassinated by the monk Lhalung Pelgyi Dorje. His son, Osung, ruled until around the end of the century, when the empire collapsed.