Los Illuminados ("The Enlightened" in English) is a religious cult in Spain known to worship the Plaga, a parasitic arthropod that can survive on their own, but they can also attach themselves to central nervous systems in animals. The insignia for the group is a symbol which looks like a stylised Plaga parasite.
The Plaga itself causes eyes to glow red and they also increase strength and vitality. However, they cause blood vessels to swell, causing internal bleeding, vomiting blood, fainting and convulsions. They can also push through the body if it is exposed and directly attack an assailant.
As previously noted, Los Illuminados is a cult and as such a lot of their history is fabricated. It is portrayed as an ancient religion. In reality, it is simply a vehicle to spread the Plaga parasite amongst more and more people.
It was established in the 1990's by Osmund Saddler, who discovered the Plaga and eventually found a way to produce new specimens. With all members of the cult implanted with a parasite, Saddler himself was implanted with a Dominant Species Plaga, which was essentially an enhanced parasite which allowed him to control the lesser parasites.
Members of Los Illuminados retained their intelligence once implanted with a Plaga, and as such they performed regular tasks such as breeding animals for food, tending the land and living in villages with families. However, they also attended cult rituals and sacrificed people.
The main goal of Los Illuminados was to infect the entire world population with the Plaga - the plan was to kidnap Ashley Graham, who was the daughter of the President of the United States at the time, infect her with the parasite and then send her back to US soil, which would put her under Saddlers influence. Then, from there gradually take over the USA and then the rest of the world.
After the deaths of Osmund Saddler and all of his lieutenants, the group destabilised but some remained and helped conduct research on a new virus named the A-Virus, which causes similar effects to the t-Virus, but with less brain damage and less dramatic necrosis. However, a vaccine was quickly developed and spread across the world which rendered the virus harmless.
It is not known if any other Los Illuminados members survived any further events, but it is most likely none have survived without a master.