The necessary qualifications of a Terton
Dudjom Rinpoche was recognized as the incarnation of Dudjom Lingpa (1835-1904), whose previous incarnations included the greatest masters, yogins and panditas such as Shariputra, Saraha and Khye’u Chung Lotsawa. Considered to be the living representative of Padmasambhava, he was a great revealer of the ‘treasures’ (terma) concealed by Padmasambhava.
In a text by Dudjom Rinpoche, the Dudjom Chojung, History of Dharma, it mentions the three lineages from Padmasambhava required for the Terton, in addition to the three lineages already required, the Choba Sumdon, for Mahayana tantric Dzogchen teachings. These additional lineages are Melong Uche Chopa, where the Guru makes aspirations for the Terton. Kabab Lungten gi Chopa, where the Guru identifies these special people for the specific special task and then empowers
them. Khandro Tercho ki Chopa is where the Guru empowers various Khandros or ḍākinīs to become keepers or protectors of the Da-yig which seals his important teachings, and thus invariably tying the Khandro’s destiny to that of the Terton. So it isn’t any ordinary Buddhist practitioner, it’s not even any high Lama who gets access to the symbolic script. They have to definitely have those three extra lineages from the Guru himself: the person has to be wished for, he has to be chosen and empowered and prophesized by the Guru himself.”
As per HE Gangteng Tulku Rinpoche, (the 9th body and activity incarnation of the famous Terton, Pema Lingpa) says in the 2019 documentary:
“To read the ḍākinī symbolic letters, one needs to blessed by the body, speech and mind of Guru Padmasambhava. If one is not a terton (treasure-revealer) no matter how educated one cannot decipher the ḍākinī script.”
Soure: Dakinitranslations