The Vowsin between birth and rebirth

In the time of Buddha Woesung (sangs rgyas 'od srung), the protector was born in an aristocratic family. When he grew up, he took Ge-nyen vows (dge bsnyen, religious vows taken by laypeople as distinguished from those in the monastic order) from Buddha Woesung and achieved the Bodhisattva way of life. At one time, he stole a goat from his neighbour, took it to the cemetery, and there killed the animal and ate its meat. He wore the goat's skin, killed all males he came across, and fornicated with all the females he came across. Remaining thus, he one day took the meat of a deer that had died after consuming poison. As a result, he too died.   

After transmigrating from that birth, he was born the son of a demon called Zamin Karma (gza' smin dkar ma). He grew up to be of unrivalled power and daring and killed a countless number of sentient beings. Palden Tamdin was angered by this and flung his handstaff at him. It struck him in the head, which cracked, and his soul passed into the Pure Realm (dag zhing).  

When Lobpon Pema Jungney sat meditating in seclusion in a cave at a mountain called Yarigong (gya' ri gong), a white man riding a white lion appeared in the afternoon of one day, holding in his hand a nine-pointed Vajra and wearing a felt hat. He dismounted and, without removing his hat, prostrated himself three times before the Lobpon and then asked, 'Do you recognize me?' Lobpon pretended that he did not and asked him who he was. He told him everything in detail, and Lobpon was greatly pleased. After that, he oath-bound him by putting the texts of the pledge on his head. He, on the other hand, vowed never to deviate from his oath. He offered lobpon his life-heart and pledged to protect the Dharma. Later, when Lobpon came to Tibet, Dorje Legpa received him. Lobpon once again bound him by oath to protect the Tantric Dharma. The details are given in 'Lha 'dre bka' thang'. 

Alternate lineage story

There are stories in various other texts on how Chagna Dorje or Sangdag subdued Dorje Legpa (with other names) and made him the protector of Dharma. For example, according to the thirteenth chapter of a text called the Lineage of Dorleg Dawa (rdor legs zlaba'irgyud), the history, once upon a time, one of the Five Daughters of the World (sridpa'ibumolnga), named Chezhemukhaley (chezhe mu kha le), and the demon Yangje Lamey (bdud po yang rjebla med) gave birth to Dorje Legpa. When he grew up, his parents consulted a soothsayer on the meaning of a black mole near the heart of the youth. The soothsayer said it was an extremely good sign and instructed the parents to at once get him empowered under Chagna Dorje. The Mother took her son to the Sangdag (a reference to Chagna Dorje) and gave him her reasons. Sangdag empowered him and gave him the name Dorje Legpa.