Scathan the Approver is a member of the Celestials who is held in high regard by both Eternity and The Living Tribunal. His exact role in relation to the other cosmic beings is unknown, but he seems to function as a kind of committee secretary. In the words of the Living Tribunal, "Scathan the Approver comes only to observe and record my judgement..."
He was contacted by the Living Tribunal to help deal with the situation regarding Protege. During most of the trial, he was a silent witness, holding Protege, the Beyonder, and the Guardians of the Galaxy, while the Tribunal, Eternity, and the Hawk God argued the case. The Beyonder clearly held Scathan's power in deep respect.
Protege, on the other hand, did not. He copied much of the power of the assembled beings and attempted to become the new One-Above-All. At that moment, Scathan released a large blast that knocked many of the assembled beings down; he did not approve of the situation. When they all got back up, Scathan had trapped Protege in a muzzle. The Living Tribunal then created an Eternal Hourglass and trapped Protege within it. Scathan approved of the sentence.