The Fulcrum is also the Bartender who runs The Vestibule, a swinging bar where Eternals go before they either return to a newly regenerated body or head off to Lacuna (The Afterlife). Said to be "all-powerful" and "all-knowing", the Fulcrum is likely an aspect, manifestation, or alternate name of the One-Above-All.
The Fulcrum is an incarnation of Jack Kirby, the well known author who literally created the Celestials and the eternals.
Apparently he makes excellent cocktails and has a great sense of humor.
Powers and Abilities
The Fulcrum is all-powerful (omnipotent) and all-knowing (omniscient).
The Fulcrum is possibly one and the same with the One-Above-All, or an aspect or manifestation of the latter.