Pah-wraiths
The Pah-wraiths are non-corporeal beings, enemies of the Bajoran Prophets. Bajoran religious texts relate that the Pah-wraiths once resided in the Celestial Temple alongside the Prophets. However, for reasons unknown, they were banished to the Fire Caves on Bajor. According to ancient Bajoran texts, they were "false Prophets".
The Pah-wraiths typically take the form of fire spirits (from which they get their name). All of the so-called "wormhole aliens" are vulnerable to chronitons. This was discovered in 2373, when a Pah-wraith took over the body of Keiko O'Brien and attempted to destroy the Prophets by firing a chroniton beam directly at the Bajoran wormhole, but was foiled and destroyed by Keiko's husband Miles O'Brien. (DS9: "The Assignment") They are very similar to the Prophets, for they can appear to corporeal beings as people they know. (DS9: "'Til Death Do Us Part")
In the same year, one of the Kosst Amojan took over the body of Jake Sisko in order to fulfill the ancient prophecy of "The Reckoning". The entity was driven out after Kai Winn Adami flooded the station with chroniton radiation before the battle was completed. (DS9: "The Reckoning")
In 2374, Gul Dukat released a Pah-wraith from an ancient artifact, which then took over his body and then used him to get to the Orb of Contemplation on board the space station Deep Space 9. Jadzia Dax happened to be in the shrine at the time, and was fatally wounded by the Pah-wraith. The Pah-wraith was then released into the Orb, allowing it access to the wormhole and collapsing the entrance on the Alpha Quadrant side, starting a war between the Prophets and the Pah-wraith. (DS9: "Tears of the Prophets")
In 2375, Benjamin Sisko received visions from the Pah-wraiths, via a quest for the Orb of the Emissary, in an attempt to confuse him from what the Prophets wished him to do. They failed and Sisko opened the vessel containing that orb, reopening the Bajoran wormhole. (DS9: "Image in the Sand", "Shadows and Symbols")
The imprisonment and release of the Pah-wraiths was detailed in the Book of the Kosst Amojan and the legend of the koss'moran. Followers of the teachings of the Pah-wraiths joined the Cult of the Pah-wraiths. Dukat posed as the Emissary of the Pah-wraiths in 2375, on board the abandoned Cardassian space station Empok Nor. (DS9: "Covenant")
In the same year, Kai Winn discovered that it had been the Pah-wraiths that had been communicating with her, rather than the Prophets. (DS9: "Strange Bedfellows")
Dukat, in disguise as Anjohl Tennan, then convinced her that the Pah-wraiths are the true Prophets, and that they must be released from the Fire Caves. She agreed, and consulted the Book of the Kosst Amojan. (DS9: "The Changing Face of Evil")
Later that year, Sisko tried to stop the Pah-wraiths. However, they resurrected Dukat with near-omnipotent power. Dukat revealed the Pah-wraith's plans to Sisko: to spread over the Alpha Quadrant, leaving it burning. In order to stop them, Sisko threw himself, Dukat, and the Book of the Kosst Amojan into a fire pit, sealing the Pah-wraiths forever in the Fire Caves. (DS9: "What You Leave Behind")
