According the Worldmind, the Luminals are the equivalent to the Avengers. They are are also a guarding force of Knowhere. Their leader is Cynosure.
On Knowhere, the Luminals had many run-ins with the Guardians of the Galaxy including many misunderstandings, as the Luminals strictly follow the rules set by Chairperson Gorani.
When the Luminals investigate the Fault without the cooperation of the Guardians, they unleashed a creature from another dimension that's only purpose was to cause death. It killed the Luminal Massdriver before Moondragon was able to take the creature inside of her and control it psionically. The Luminals demanded justice for the death of their teammate and detained Moondragon. Before a hearing could take place, Cynosure and Moondragon (who were cuffed together) were kidnapped by the Matriarch and the Universal Church of Truth.
The Luminals and the Guardians teamed up and successfully rescued their teammates. After this, the Luminals and the Guardians put their differences aside, the Luminals even stating they would leave Knowhere if the Guardians were cast out.