They are awakened from their stasis as a result of the Stone of Jas being used and the death of Zorgoth, who appeared to have had them imprisoned in strange tubes. Provoked by the misuse of the Stone, which they are bound to by Jas, the dragonkin plot to take their anger and pain out on the world.
Gallery
The strange tube as they appeared when visiting the vault during Dragon Slayer II.
The dragonkin awaken in the Lithkren Vault.
Trivia
Strisath's stasis chamber is found by the northern entrance to the adamant dragon area, but is freed offscreen.