A set of prophecies written three thousand years ago by the Bajoran Trakor after an Orb encounter, one of which seems to foretell disaster for a joint Cardassian project at the wormhole.
Trakor was an ancient Bajoran who met an Orb and wrote down what he saw. His prophecies are a respected part of Bajoran scripture, and several concern the Emissary.
They are central to Destiny in 2371. Three Cardassian scientists arrive at Deep Space 9 to help set up a communications relay through the wormhole. Vedek Yarka warns Benjamin Sisko that Trakor's Third Prophecy speaks of three vipers returning to their nest in the sky and of a sword of stars that will burn the temple gates open for ever. A comet duly appears and threatens the wormhole.
Sisko at first dismisses the warning, to Kira Nerys's discomfort. The prophecy proves true in an unexpected way. The vipers are fragments of the comet, and the trail they leave through the wormhole creates a permanent channel for the relay.