The primal monitor, simply put, is the canvas the writer uses, seeing as the red circle above is not the primal monitor; the blank, empty white is. He first appeared in the issue of Superman Beyond #1. He is so infinitely vast that entire creations are like nothing to him, logic, reality, creations fall short of him. Mandrakk referred to it as the 'Overmonitor'. In the Superman Beyond series, he is told that he was the creator of the Monitor and the Anti-Monitor and them together, individually comparable to The Spectre, was only a tiny probe of his. He is even less known than The Source.
Powers and Abilities
The Primal Monitor is the canvas of all writers, and its powers include Omnipotence, Omniscience, and Omnipresence. Though this is not fully proven yet as the Overmonitor have been interpreted in various ways throughout DC Comics. Grant Morrison made it the God of DC, Whilst Neil Gaiman's interpretation of it basically calls it "the canvas where everything is drawn out", and may even contend with another being of similar power, The Presence.