So the idea was that this is the original tree that existed in all spaces. When the leaves and branches began to die the travellers capped them in gold and crafted new leaves to preserve the energies of the tree. Portals were crafted from the tree allowing travel to other spaces.
The crystaline enemies could be people who travelled too much, or people who travelled with forbidden items for example metal ore. In game i'd imagine their polygons would always be slowly rearranging as they 'shift' into positions instead of walking normally.
Process was: Blockout some big shapes/initial concept in C4D > Find a nice background location & take screenshot in the game Valheim & then Paint over everything in photoshop.