Los Illuminados (From Spanish meaning "The Illuminated Ones") was a cult operating in an unknown rural region in Spain.
It was created some time around the 1700's where they worshiped the "Las Plagas" (Spanish:"The Plagues"), a parasitic organism with the ability to control it's hosts.
The 1st Castellan of the region outlawed the cult and sealed the Plagas in a cave system beneath his castle.
Eventually under the rule of the 8th Castellan, Los Illuminados now under the rule of Osmund Saddler, were allowed to mine the area, having either tricked or converted Salazar to it's cause, effectively occupying his castle which acted as a base for the cult under Saddler.
By the time the Plagas were found however, they were all dead and seemingly useless. However Plaga fossils (suggesting they could be millions of years old) were found to be still carrying living spores and it was these spores that first infected the miners, becoming full fledged Plagas after many years of development. Likely using these first Plagas, Saddler perfected the ability to reproduce the organism and took to implanting Plagas eggs into new hosts.
The entire Los Illuminados were soon inplanted with Plagas along with much of the local population who had joined the cult. Saddler himself was implanted with a Master Plaga and as such has direct control over the others using lieutenants with similarly augmented Plagas to monitor and direct the Ganados on the ground. Any who resisted the Plagas were executed or used as research in the cults genetic manipulation experiments.
The villagers then returned to life as normal as they could, farming, attending cult services at the local church, acting as guards for Salazar's castle or working the mines while the cult zealots engaged in dark rituals and sacrifices in the name of Saddler.
Eventually, American agent Jack Krauser, while secretely working for Albert Wesker arrived at the village in search of the parasite. He was later used to kidnap Ashley Graham, daughter of US President Graham as part of an Illuminados plot to do no less than take over the entire world by infecting Graham and returning her to her father in order to infect the United States executive. Plan B was to use Saddler's paramilitary militia to infiltrate the United States and sow discord from within, likely gaining converts to Los Illuminados as they went.
Los Illuminados is believed destroyed with the death of Saddler and the Master Plaga.