That's not my understanding from what I've read.
"The shadow realm may be a place, but it is not a part of any plane or world. It stretches from the very pit of this universe, below even the lowest planes, and reaches all the way to the highest, to Gielinor itself. Along the way its tendrils reach out and touch many worlds, wrap around them, and those worlds too are said to have 'shadow realms'
"What none can see whose lives do not span the breadth of eons as ours do, is that the shadow realm is spreading. When first we were subjugated by the stone, the shadow barely reached the lower planes. With each millennium that passes, the planes gradually fill with shadow, until it spills out across the universe covering more and more worlds. Having reached even Gielinor, I do not know what if anything can stop it from filling the universe entirely."
As Noted by the Dragonkin, the Shadow Realm is expanding thus I still believe what I've said to be valid. If the Shadow realm is expanding, the elder gods can't expect to make their planets in the same exact location each time since Shadow Anima from the Shadow Realm is poison to them
As for "They simply managed to close the hole on Gielinor with the Codex."
You are thinking about teleportion to the Shadow Realm as if it was any other location such as Zanaris.
From my current understanding, the Shadow Realm is an expanding overlay akin to what many real life cultures see the spirit world as. There aren't just breaches forming, it is actually growing and occupying the same space parallel to the game's universe.
We also have evidence that the elder gods make their worlds on higher and higher planes because, Freneskae, their previous perfect world, is the lowest positioned of them all while their current perfect world, Gielinor, is the highest positioned.
With that said, it should be obvious that the Shadow Realm is growing, the Dragonkin even confirm it
13-Jul-2021 05:39:51