when you're in hunter's dream in BB you can see the other stems all around

lordran is built on top of a tree

the lands between are a spiral around the erdtree

i think elden ring tells the early prehistory of lordran, bloodborne shows the future of it. they build lordran on top of the tree and then it becomes yharnam over 1000s of years.

the thing is each player's game copy represents another copy of the erdtree, another world history. thats why theres millions of stems.