They intended to use the Exomorphs as a form of work force and beasts of burden in their empire which was over three thousand years ago. However, they lost control of the creatures when one of the Exomorphs called the Archeopendra gained sentience. Using this intelligence, it succeeded in destroying the ancient Idryll empire but not before they were stopped and placed in a deep slumber. These actions collapsed the Idryll civilization fell into a dark age which regressed into a pre-warp society where science and technology were lost to them. The Attrexian race was later involved in destroying the remaining Exomorphs and believed they had destroyed the remaining manufacturing facilities but they simply repaired themselves and awaited to be activated.
At some point in the year 2380, an ancient Idryll Exomorph manufacturing center on Theta V was discovered by a group of Idryll archaeologists. They were determined to prove to the Attrexian race who were controlling them that they were a much older society and many Attrexian colonies were actually ancient Idryll worlds. Once inside, they discovered the Exomorphs where the Idryll Separatist member Krindo activated them. Once awakened, the creatures went out of control and trapped the scientists in the facility while several of the creatures themselves spread into space. There, they began attacking an Attrexian space station and the Federation Starship USS Dallas where they killed many of the crew whilst they went about their rampage through space.
Their actions were, however, noticed by Starfleet who dispatched the USS Enterprise-E to investigate the disappearance of the Excelsior class vessel, USS Dallas. Deploying the Hazard team, Starfleet encountered the Exomorphs for the first time and managed to rescue some of the crew. Their findings later determined that the creatures also attacked an Attrexian space station leading to the second encounter with the creatures. Despite the loss of several Starfleet and Attrexian personnel, they were successful in driving off the Exomorphs. In the aftermath of the battle, the crew of the USS Enterprise studied the remains of the creatures and learnt of their genetically engineered nature.
Tracking the propulsion trails left behind by the creatures, the USS Enterprise arrived in the Vioc Theta V system in order to learn more about this threat. Once there, they learnt from a group of Idryll archaeologists that the creatures were called Exomorphs and were bio-genetically modified by the Idryll to serve as beasts of burden. However, they became violent for reasons unknown to the scientists who had become trapped in the manufacturing outpost where they successfully created some of the more peaceful templates of the creatures. Alexander Munro was later successful in shutting down the facility and preventing the creation of more Exomorphs within it by destroying the incubation chambers after which the history of the animals were explained to the crew of the USS Enterprise. The Idryll scientists were detained and their work stopped in order to prevent anymore Exomorphs from being created.
However, this was not the end of their threat as the Attrexian colony in the Taravar system was under attack by the beasts. They began swarming Taravar VII where the first swarm caught the colonists off guard after which they massacred the security forces. The USS Enterprise arrived after receiving the Attrexian distress signal at which point the third wave of Exomorphs struck the colony. The creatures were successful in knocking out the local defense grid. The Hazard team was deployed to the colony to fight off the Exomorph infestation which had been commencing a siege on the planet for three days. After saving the few remaining Attrexians, they learnt from Inigor that his son Krindo had activated another Exomorph manufacturing plant and dispatched the creatures to attack the Attrexian colony. With the USS Enterprise was disabled in an Idryll attack, the Hazard team was dispatched to a nearby ancient Idryll outpost which contained an Exomorph factory.
On this second factory world, the Idryll Krindo coordinated the Exomorph attacks but when he attempted to call them off the Attrexian colony in fear of his father's life, his commands were not accepted and his father perished. He discovered that he had lost control over the Exomorphs and helped Alexander Munro destroy the facility. It was later discovered from Krindo that there was a single primary facility that controlled all the others and the Exomorphs called the Master Control Facility. He believed that someone had uncovered it and overrode his control over the creatures. Learning that the only other person who knew of the Idryll sites was the Ferengi Omag, they discovered from this source that it was the Romulans who had learnt of the Exomorphs. Traveling to a secret Romulan base, Alexander Munro learnt of a faction called the Empty Crown that sought to use the Exomorph's as a doomsday weapon against the Federation. Thus, began a desperate search by the USS Enterprise for the Master Control Facility.
The base was present within the Romulan Neutral Zone where a faction of the Romulan Star Empire took control of it with the intention of using it as a weapon of mass destruction against the Federation. Under the command of Suldok, the Empty Crown attempted to engineer an intrusion from Starfleet and thus allowing the Imperial Romulan Senate to empower them for war. Their plans and the Exomorph threat ended when Alexander Munro destroyed Archeopendra and the Master Control Facility. This stopped creatures which could become a threat to the Alpha or Beta Quadrant.