Eternity puts up a fight against Thanos with the IG, pretty impressive since the other powers of the universe got all owned by him easily.. (please log in to view the image)
"Wolds within Worlds, Dimensions folding into themselves,
Entire UniverseS being born, and collapsing into ruin,
and yet I sense that ALL this -- is but a fraction of what Eternity is,
the core, the Heart of Eternity's being ... here All Energy, All Matter, lies,
I will detonate Eternity's Heart --- triggering another Creation event,
Re-Birthing every being and thing in All the UniverseS"
eternity is also the one who spawned the six friendless, ^notice in the above scan entropy and Epiphany are children of eternity, this is also confirmed in another scan when Epiphany refers to him as "our father"
captain marvel v5 #25: the seven friendless (since eternity is among them, but seeing how 2 of the referred to eternity as their father i would assume the others are also his children):
same issue: whole universes and dimensions are only the merest fraction of what eternity truly is, and dormammu stole eternity's power (due to a cosmic shift) and re-birthed all beings and all things in all universes
fantastic four annual #2001: multi-eternity (or a eternity as a whole) is the embodiment of the whole multiverse (which consists of infinite universes and as the scan shows each universe is infinite or boundless)
Strange tales v1 #147: strange wonders if eternity was destroyed in that fight (which is revealed later to be incorrect) and that dormammu was destoryed
Dr. Strange v1 #180: eternity is revealed to be alive (note that there is a mistake in the scan since the dormammu vs eternity fight is referenced to be in strange tales #138 when in fact it is in issue # 146)
defenders v1 #92: possibly the first appearance of eternity as a whole, the writer may not have intended it but it seems so. Eternity explains that it took mortal bodies which were scattered across the multiverse and then called them back into his totality (which leads me to believe this is eternity as a whole). but 3 of his selves didn't return which means that eternity is incomplete and threatens all existence (later in the issue it's revealed to be the entire multiverse)
same issue: the threat is revealed to be multiversal in scale (this further proves that this is multi-eternity since the multiverse is beng destroyed because eternity is incomplete if it was only 616 eternity only 1 universe would be threatened)