On or about Cyberdate 90354.61, while gathering parts in a crypt to restore two dead Seekers, a group of Decepticons encountered a long-dormant nanovirus that was re-activated by their body energy. The nanovirus mutated, causing different effects in each Decepticon. Plunder and Sunder were among the first infected, as well as the Autobot Jetfire. The exposed Decepticons then infected Mixmaster and Bombshell, as well as other several other Autobots and Decepticons.
Once the virus activated, it placed many of the infected under control of the ancient techno-organic known as the Dweller. In seeking the Dweller, nano-virus-controlled Bombshell sought a path to its Hiberation Chamber through the tunnels beneath Kalis, only to be stopped by the Centurion droids. When the Weatherbots entered the Kalis tunnels, the Centurion droids attacked them. During the fight, the Dweller was released from its subterranean prison.
When the Dweller’s thrall Hubcap was taken into Darkmount, the Dweller followed, laying siege to Polyhex. Mixmaster returned to Polyhex to "recruit" more followers for the Dweller, only to be subdued and cured by Starscream. In return, Mixmaster promised the help of Devastator against the Dweller. However, with Hubcap's assistance, the Dweller took control of Polyhex and drained the energy from the polity and its smelting pools.
On Cyberdate 90642.28, Hubcap announced that he intended to surrender himself to Decepticon authorities. However, once they arrived, Hubcap stated that his "master" (the Dweller) was "done here." Soon after, Hubcap trigged bombs his forces had planted around Polyhex and destroyed the center of Polyhex, killing any remaining refugees in hiding and severely damaging Darkmount and Decepticon HQ. The Dweller was then lured into attacking a the Quintesson ship there. The Dweller invaded its Space Bridge Nexus and destroyed all the Quint ships connected to the network, ending the current Quintesson attack.
The Autobots were able to reverse the effects of the Dweller virus on the Weatherbots and others, using a modified version of a cure developed by Jetfire and Starscream. The Dweller then disappeared until recent independent experiments by Goth and Ratchet freed the Dweller from its interdimensional trap.