First Ancestral Race
The First Ancestral Race are the mysterious god-like progenitor aliens, never seen during the course of the series, who created the beings known as "Seeds of Life" to seed the galaxy with life forms. Two such Seeds of Life were Adam and Lilith. Two types of Seeds were created; those transported to their destinations in massive vessels dubbed "White Moons", similar to Adam, and those transported in massive vessels dubbed "Black Moons", like Lilith. On planets which White Moons landed on, the Adam-like creatures would give rise to Angel-like creatures which became the dominant species on the planet. On planets which Black Moons landed on, the Lilith-like creatures would spread LCL, the "primordial ooze" from which what humans would consider "normal" terrestrial life forms would evolve, culminating (after millions of years of evolution) into human-like life forms.
However, a White Moon and a Black Moon were never meant to land on the same planet. Adam was the Seed of Life which originally landed on Earth, but 4 billion years ago the Black Moon containing Lilith violently collided into Earth, in the event later dubbed "First Impact". Thus, humans and Angels cannot co-exist and were put on the path to one day having a confrontation for mastery of Earth.
The First Ancestral Race also created the artifact known as the Lance of Longinus. A Lance was sent along in each White Moon and Black Moon, as a countermeasure should any of the Seeds ever go against their projects.