The One Above All created the omniverse itself in the beginning of creation and after creating it, created the Living Tribunal to oversee the multiverse and act as it's overseer the Multiverse and act as it's sole and highest authority as well as it's overseer.
When Beta Ray Bill died in his battle with Asteroth, she first appeared presumably as a mysterious, white robed man who then used his power's to revive the dead gladiator.
When the Fantastic Four journeyed beyond the plane of existence, they entered the realm of the One Above All where he was taking the form of Jon Stevens. The One Above All appeared in front of a pregnant Susan Storm who was fearing for his life at the hands of the Silver Surfer gave her hope by healing Reed Richards severely damaged face and afterwards sent them home.
He made an appearance as a homeless man in the street advising Peter Parker known as Spider-Man to see his dying Aunt May. He also comforts him that he should just let her die because death is a natural part of life. Unfortunately, Peter does take not her advice.
When the Thing died, the One Above All appeared and congratulates the Fantastic Four for exploring the multiverse whom the latter promised extraordinary new wonder's in the later years and later afterwards resurrected the Thing.
