Revealed Treasure (Terma) is a concept originating in Tibetan and Himalayan Buddhism with the Nyingma Tradition. It is a belief that Padmasambhava and a few of his principal disciples concealed both religious teachings and sacred objects throughout the Himalayas and Tibet to be discovered by future generations when necessary.
"In the Nyingma Tradition, there is the lineage known as Terma (Treasure), which comes from the great Master of Uddiyana, Padmasambhava, who, after coming to Tibet, manifested all the many common and uncommon Dharma teachings for the King (Trisong Deutson) and his followers. They then gathered these together in order to protect and preserve the Dharma for the sentient beings of future degenerate times, and conceal them as mind and earth treasures. At appropriate times as a source of benefit and happiness for sentient beings and the Dharma.
There are also many renowned Lineages of Pure Visions and of 'Ear Whispered Transmissions' existing in both 'new' and 'old' Secret Tantras.
Some scholars have questioned the validity of these Holy Treasures, but they need to examine the purpose and necessity of Terma. That these Treasures are the authentic Dharma is established by the three standard criteria of logical argument. So please be careful, because criticizing the Dharma with anger is a grave fault and will only cause your defilements to increase, becoming thick and heavy.
The "One Hundred Thousand Verses of the Prajnaparamita Sutra" etc. were Treasures revealed by Nagarjuna. Furthermore, many great Saints discovered and revealed Treasures of Sacred Writings of the Secret Tantra from the Stupa of Dhumathala in Uddiyana. And so, even in the Noble Land of India, we find Treasure revelations (Terma) occurring. There are many logical arguments concerning this, but I shall not present them here."