A Destiny Stone (ホーリーストーン Hōrī Sutōn?, lit. "Holy Stone") is a relic that appears in Digimon Adventure 02. It is a sacred rock formation that regulates the boundary between the Digital World and the Real World, and is usually bound with a Holy Ring.
Digimon Adventure 02
The seven Destiny Stones act as the "cores" of the Digital World, and when they are tampered with, the Digital World suffers. As they are destroyed, the boundary between the Digital and Real Worlds falters, causing Digimon to appear in the Real World.
Destroying the Destiny Stones is originally one of Arukenimon and Mummymon's many schemes to break down the barrier between the worlds. Mummymon and Arukenimon first come across a Destiny Stone and begin attempting to destroy it. They are delayed by the DigiDestined, who attempt to stop them from further damaging the Digital World. At the same time, BlackWarGreymon is having a discussion with Agumon about life. However, the discussion is cut short when several blows are made to the Destiny Stone, causing BlackWarGreymon—for unknown reasons—a great amount of pain. BlackWarGreymon flies away from Agumon and destroys the Destiny Stone, despite the attempts to stop him by the DigiDestined.
BlackWarGreymon proceeds to destroy all the Destiny Stones, to the delight of Mummymon and Arukenimon. The DigiDestined try and fail to stop him every time, but one time come close when Angemon uses the power of a Destiny Stone to digivolve to MagnaAngemon. MagnaAngemon is nearly able to defeat BlackWarGreymon, but dedigivolves when BlackWarGreymon manages to destroy the Stone anyway. Initially BlackWarGreymon's motive to destroy them is the pain he is caused when they are tampered with; in Destiny in Doubt a new motive is discovered. In Episode #34, when BlackWarGreymon destroys a Destiny Stone, a (pained) Digimon appears in the sky briefly. BlackWarGreymon—in belief that his destiny is to only destroy, and become the strongest Digimon, the conversation with Agumon forgotten—believes this Digimon to be his only worthy opponent. From then on BlackWarGreymon destroys the Destiny Stones to ultimately battle this Digimon. This Digimon is revealed to be Azulongmon, who appears when the DigiDestined use their Digivices on the last Destiny Stone. He explains things to BlackWarGreymon, who gives up his quest to destroy the Stones, then goes off to plant seeds for new Destiny Stones to replace those that had been lost.