The Kosst Amojan or Koss'moran was, according to Kai Winn Adami, "the Evil One. A Pah-wraith banished from the Celestial Temple." According to Shabren's Fifth Prophecy, the Reckoning was to bring on the rebirth of Bajor, explaining that "if the Evil One is destroyed, it will bring a thousand years of peace. The Golden Age of Bajor." (DS9: "The Reckoning")
It was thought to be a Bajoran legend that told of false Prophets who were cast out of the Bajoran Celestial Temple. The Bajoran word Koss'moran came from the verb kosst that meant "to be," and amoran, which meant "banished." (DS9: "The Assignment")
In 2374, the Kosst Amojan inhabited the body of Jake Sisko in order to bring forth the Reckoning. The possession was ended after Kai Winn Adami flooded the station with chroniton radiation. (DS9: "The Reckoning")
According to the script for "The Assignment", the following pronunciations were provided:
- amoran: "uh-MORE-un"
- Koss'moran: KOSS moe-RAN
- kosst: "COST" 
Ambiguity existed as to whether the Kosst Amojan was an individual or another name for the Pah-wraiths. Kai Winn referred to it from an ancient prophecy as an individual in "The Reckoning"; however, in "Shadows and Symbols", the Sarah Prophet referred to the Pah-wraiths that were defeated in that episode as the Kosst Amojan. Furthermore, in the final episodes of the series, Kai Winn herself referred to the Pah-wraiths in the Fire Caves as the Kosst Amojan and it seemed to imply that the Kosst Amojan was in fact the entity that possessed Dukat during his duel with Ben Sisko. It was possible that the individual Kosst Amojan (whose whereabouts remain unknown) entered the wormhole with the Pah-wraiths at the end of "Tears of the Prophets" and subsequently both were destroyed, or the prophecies as Winn knew them in "The Reckoning" were wrong and the Kosst Amojan was in fact the Prophets' name for the Pah-wraiths. Another possibility might be that it was a group of Pah-wraiths.
In its entry on the Kosst Amojan, it is viewed as a single entity by the Star Trek Encyclopedia (4th ed., vol. 1, p. 440). The authors of this reference work, in the note to the entry, raised the possibility that the Kosst Amojan was a term might refer to all Pahwraiths as a group.
The only definite appearance of the Kosst Amojan was portrayed by Cirroc Lofton.
The group was originally named the "Koss'moran" but, according to the Star Trek: Deep Space Nine Companion (pp. 389-390), for their reappearance in "The Reckoning", René Echevarria altered the name (with Ira Steven Behr's approval) because he didn't like the "moron"-sounding part of the original name. Both that and "Kosst Amojan" mean "to be banished".