The Helm of Ieldis was a Sith Lord Ieldis creation in the years prior to the Great Hyperspace War. It was a helmet imbued with the powers of the dark side. When worn by a Force-sensitive Dark Sider, the Helm was capable of converting negative emotions like grief, anger and misery into Dark Side energies capable of driving sentient beings into a homicidal frenzy.
It was a Sith artifact crafted after years of study by Ieldis into the nature of conflict between people and what drove them into throwing their lives away. The Helm was capable of manipulating negative emotions like grief, anger and misery and channeling into Dark Side energies which drove entire armies into a homicidal frenzy. At some point after the destruction of the Sith Empire, the Helm was hidden on the world of Sarrassia by the Grumani Hierophants. They hid it in an underground temple beneath Mount Diligence. Later, it was moved to Skarpos, a bleak desert world where the Grumani had a temple in the Morbollon Mesa.
During the Republic Dark Age, a University of Sanbra research team began a preparations for a scientific expedition to locate the Helm with the cooperation of the Jedi Order. The Sith Lord Odion raided Sanbra, and learnt about the existence of the Helm. He then captured the researchers on Aquilaris Minor and conscripted them into his top-secret Project Pandemonium which aim to seize the relic before his Sith compatriots could lay their hands on it. This research team included the archaeologist Mercia Holt and her husband Aron Holt, the parents of Jedi Knight Kerra Holt. In 1038 BBY, their last recorded trail stopped at Sarrassia. It was later revealed that the Holts had sacrificed themselves in an attempt to destroy the Helm by triggering an explosion. While the surrounding Grumani temple chamber was badly damaged, the Helm survived since it was a Sith artifact.
In 1032 BBY, Kerra infiltrated the Novitiates, Odion's elite Force-sensitive corps of acolytes, using the alias "Mercy." During the Invasion of Sarrassia, she learnt from Aunt Zoojoo that the Helm of Ieldis had been relocated earlier to Skarpos, a war-torn planet in Lord Malakite's realm known as the Menagerie. During the Second Battle of Skarpos, the Helm was located by Odion himself who had taken a shuttle to the planet. He found the Helm of Ieldis within a cave excavated by Grumani Hierophants, beating his own team of hunters. Meanwhile, Kerra located the cave, damaging the airspeeder carrying her fellow hunters so that they could not follow her. Within the interior chambers, she located her mother Mercia's satchel but found no sign of her parents.
Kerra was then attacked with Force lightning by Odion himself, who praised Kerra for leading him to the Helm before acknowledging her true identity. He then announced that she would be the first to witness it in action. Odion would then used a captive Kerra to activate the Helm of Ieldis; she had succumbed to grief after learning about the deaths of her parents. Odion would use the Helm to annihilate three entire armies on Skarpos, forcing his rivals Daiman and Malakite to flee into hyperspace. A jubilant Odion then took the Helm to Vanahame, which was home to a planet-sized orphanage known as a cloister. There, he would used the misery and anxieties of the captive children to unleash the Helm on a galactic level to destroy all sentient life in the galaxy to fulfill his desire to be the only sentient being.
During the Battle of Vanahame, Odion shut down the lights in the cloister, bringing about panic and dismay in the children, and thus obtaining the energies to power the Helm. He then started to use it to bring about a wave of mass murder throughout the Grumani sector; however, he was thwarted when his General Beld Yulan, who had been convinced by Kerra to turn against him, freed the captive children, and the rush of positive emotions such as joy and happiness caused the Helm to malfunction and explode, destroying it and killing Odion.