The Lost Orb was a fabled Orb of the Prophets and one of many that were sent from the Bajoran wormhole to the planet Bajor in distant times. Unlike its compatriots, knowledge of this Orb became myth and it was later guarded by a mysterious order of Bajorans that lived in an isolated region of their world. Furthermore, this Orb revealed many secrets to its keepers and gave them knowledge in the arts of warfare. This in turn taught them the secrets of conflict and warfare which this secret sect of Bajorans maintained in their isolated monastery on Bajor. They did not accept anyone that was not a true believer or pure Bajoran amongst them. Furthermore, their temple had numerous traps designed to kill intruders. Those that knew their secrets were allowed to meet the leader of the order and even see the Lost Orb which was in the care of the sect for generations.
When the Cardassian Union invaded Bajor and claimed control over it, it was the keepers of the Lost Orb who planted the seeds of resistance amongst the Bajorans. Furthermore, they even provided a cadre that became the earliest resistance fighters against the Cardassian. During the Occupation of Bajor, the Resistance believed that the discovery of the Lost Orb would bring about the end of Cardassian rule of their planet. However, the Orb remained undiscovered though the stories surrounding it remained. It was the legends of the Lost Orb that prompted Kai Winn Adami into hiring the Human Lane Crockett into finding the Orb. However, he instead of delivering it to the Kai, Crockett stole the Orb and delivered it to the Aresians of the planet Ares in the Gamma Quadrant. This war-like species also worshipped the Prophets who they knew as the Wargods and taught them about the glory of conquest. The Aresians had their own Orb but desired another and thus hired Crockett to deliver them the Lost Orb. Despite initially being successful in this act, the Orb was retrieved by Major Kira Nerys who managed to escape from the Aresians.
Her faith, however, was visibly shaken as she did not understand how such a race could take the Prophet's message of peace into a religion about war. She later used the Lost Orb and gained a vision from the Orb experience where she was in battle armor and fighting numerous foes. During the vision, she encountered the former Kai, Opaka Sulan and learnt that the Prophets desired the Aresians to gain the Orb. At the time, the Aresians had assembled a warfleet and intended to invade Bajor in order to claim the remaining Orbs. It was only an alliance between Commander Benjamin Sisko leading the USS Defiant along with Cardassian warships sent by Cardassian Central Command and led by Gul Skrain Dukat. In order to end hostilities, Major Kira managed to beam onaboard the lead Aresian warship where she offered the Lost Orb to the Warlords that ruled Ares. Ultimately, the war-like species accepted the gift and returned back to their homeworld in the Gamma Quadrant. (DS9 - The Secret of the Lost Orb comics: "The Search", "Acceptable Losses", "Gods of War")