Iden was one of the intelligent holograms created by Hirogen engineer Donik to serve as prey for their holographic training simulations. He was modeled after a member of the Bajoran Militia (though his uniform had no rank insignia). As a result, he held the same belief in the Prophets as a biological Bajoran.
As one of Donik's creations, Iden was capable of learning and improving his abilities with each hunt. He was the favorite prey of his Alpha, but after repeated violent "deaths" at his Alpha's hands, Iden was able to kill him. He stole a ship and liberated the other holograms on their space station. Using this ship, Iden attacked and liberated more stations, resulting in heavy Hirogen casualties.
One such liberation drew the attention of the USS Voyager, after Donik sent out a distress signal. A Hirogen ship arrived shortly afterwards and insisted that the holograms be destroyed. As Voyager gave chase, Iden ordered that The Doctor be "liberated" from them, and his program was transferred to Iden's ship. Iden required The Doctor's help in repairing malfunctions in some of the other holograms.
Iden had a vision of a new homeworld for holograms, somewhere where biological lifeforms could not hurt them. He chose a Class Y planet and named it Ha'Dara. As class Y planets are uninhabitable by humanoid lifeforms, they would be safe. However, he required assistance in finishing a photonic field generator that could sustain those holograms he had freed. He was successful in convincing The Doctor to help him. Captain Janeway refused to provide the help they needed, so The Doctor transported himself to Iden's ship. Iden then kidnapped B'Elanna Torres so she could help finish the generator.
Initially, Iden seemed to be reasonable, but he quickly developed a messiah complex, believing that the other holograms should form a new religion around him. He attacked and destroyed a Nuu'Bari ship, taking three holograms from them, despite the fact that those holograms were mindless tools, capable of only basic tasks.
When his ship reached Ha'Dara, pursued by the Hirogen and Voyager, Iden transported the Hirogen crew to the surface. Unarmed and up against holograms they could not hurt, the Hirogen were at a massive disadvantage. The Doctor was able to disable the generator, but Iden had transferred himself to The Doctor's mobile emitter. The Doctor found and shot Iden after he refused to back down. The blast destabilized Iden's program and rendered it unrecoverable, effectively "killing" him.