In 1984 -85'
There was One Marvel Universe that was a Multiverse.
Marvel produced Other titles in the UK that involved an Omniverse,
this Omniverse was NOT part of Continuity, although Marvel published it.
In Continuity,
Beyonder WAS Everything OUTSIDE the Multiverse.
The Beyond Realm WAS the Beyonder and it stretched into Infinity:
"Meeting NO resistance in the INFINITE BEYOND"
"Evolves and Flourishes Within the New Universe, BEGAT by Beyonder's Power"
"Mortal Beings giving meaning to the INFINITY in which they dwell"
Now that you see Beyonder IS the Beyond Realm and the it takes up ALL of the Infinity beyond the Multiverse.
It's size?
"A UNIVERSE to which OUR OWN is as a DROPLET of Water to the Ocean"
OUR OWN is NOT the 616 Reality, it is the MULTIVERSE!
"Odd thing He had noticed about our Universe"
"Namely that it is Many-Layered-composed of a seemingly Endless Number of Dimensions,
indeed, it is a MULTIVERSE"
Beyonder's Universe continued to expand further,
until it became a Multiverse itself:
"Beyonder, the entity that embodied all the substance of Another Multiverse"
How much more Infinite still was his Multiverse?
I have no idea,
but if his Universe was an OCEAN,
and the Multiverse was a DROP of Water in comparison,
one can imagine, or can we?