key word: Non-canon.
Aman’thul and Eonar conceptually were originlly supposed to be a Chronos & Rhea type pairing but that never made it into any formal canon and after the revelations of the First Ones they seen further than ever to that original mythological blueprint.
I cracked the Shadowlands cosmology chart the First Ones are two snakes. 
they have many names in mythology, it’s hard to pin down one singluar myth but Shadowlands seems to have pulled a lot of inspiration for it’s setting from Greek myth, specially Metamorphoses and the Theogonies - it just makes sense to view it through a Greek and by extension Egyptian lens.
Two serpents, one living and one dead, creating an infinity symbol of an ouroboros around a central pillar of Death and Life. the coils of living snake go through Order and Disorder because they are a duality. The coils of the dead snake go through Light and Shadow, the dead snake is devouring the tail of the living snake in the sphere of Death, the living snake is devouring the tail of the dead snake in the sphere of Life.
it’s a Chaoskampf but also spiritual Alchemy.
I should also draw your attention to creation myths of the World Egg where a serpent coils at the base of The World Tree (mainly in Norse and Eastern mythology), because it’s currently very relevant to the meta narrative of 10.2 and the new World Tree. This particular serpent has many names, Jörmungandr, Leviathan, just to name a couple.
Also, Nyalotha is alive it’s not somewhere Illgynoth was ‘banished’ to it seems like it’s a living dream. If Old Gods don’t go to the Shadowlands, if they go back to where they came from then go back to where they were manifested out of a thought. Ny’alotha is less of a place and more of a sentient being. Ny'aotha is Alive?!