The Only Light was an elite sub-sect of The Other Light that had an underground base in Egypt (which became Osaze throughout the rest of the Millennial Kingdom). The base was used for weapons production and electronic espionage, and featured an underground garage and a small jail where a number of believers were kept hostage.
According to what they told Rayford Steele, their beliefs differ from the mainstream thought of The Other Light only in that they believe that God and Jesus Christ don't exist, despite the plain evidence proving otherwise, and that Satan/Lucifer, who is the only god, imprisoned himself in the pit for a thousand years in order to make a point about free will. They have no answer when Rayford calls them on their doctrine being nonsense; it is unknown whether they were feeding him disinformation or actually believed in it.
Its two named members are Ishmael and Rehema, the latter of which turned against her comrades and became a believer. As of millennial year 93, The Only Light seems to have a personnel strength in the high dozens to low hundreds.
Their goal was to kidnap Steele the day before he was due in Siwa for a revival meeting; they succeed, but Rayford manages to convert Rehema. Due to the intervention of Anis, Rayford helps the other captives drive away from the base, and makes the revival meeting in Siwa at the last minute.
It is not known what other missions The Only Light undertook on behalf of its parent organization, but by the end of the Millennium, they have at least succeeded in the weapons production part of their mission.