The Dark Side wraiths were all that were left of the six beings who were once the rulers of an unknown jungle planet which the Dark Side pyramids were located on. They were shadow forms of the ancient Dark Side priests who were still clinging to half-life through the powerful dark side emanations of the Altar of the Dark Side. They were visible only to Force-sensitive individuals.
When a group of Rebels led by a Jedi landed on the planet and made their way towards the pyramids, the wraiths attacked them multiple times; firstly when the group got within a kilometer of the pyramids they attacked simply to see how powerful the Jedi was, finding out that he was adept at the Alter aspect of the Force and knew how to use the controlling pain.
After this, they let the group advance towards the temples until they came into the plaza at the bottom of the pyramids and were about to climb the tallest pyramid which housed the altar. Here, each wraith attacked an individual person in a unique way; one of the wraiths made a Rebel think that he had been a complete failure at life and an embarrassment to his family, trying to convince him to commit suicide whereas another attempted to convince one of the Rebels that one of his companions was an Imperial spy who must be executed and yet another attempted to convince one of the Rebels that a companion had stolen his fiancé and to give him a good thrashing. The group managed to get past this attack, however and climbed the pyramid, getting to the top before being attacked once more. Just as they were about to set explosives to destroy the altar forever, the wraiths once again attacked; this time they simply used their telekinetic skills to hurl rocks at the group, the same way they had previously killed the crew of an Interstellar Survey Corps ship.
In the end, however, the group managed to defeat the wraiths by using explosives on the Altar of the Dark Side, freeing the souls trapped there and dispelling the wraiths forever.
- Shadow of the Dark Side (First appearance)