>>532268686
The princess was in another castle.

>>713215202
It isn't. We see from Enir Ilim that golden trees can be cultivated from honorable or 'graceful' dead, similar to how putrescence forms from the amalgamation of unclean death

Those trees taken to the logical extreme are the 'seed' of the Erdtree, the red blood or 'primordial matter' that became it. Imbued with the Elden Ring and an insane amount of gold/grace stolen from the corpses of Enir Ilim

A tarnished dies and drops a little golden twig. Several dozen jars makes a minor Erdtree. A colossal amount of death makes an Erdtree

At the same time it is using concepts from several other faiths in the world. The Hornsents crucible worship/tutelary deities, the shamans and grafting/merging with trees, Gelmir and ancient giant Hex magic through sacrifice, Farum Azula and the embedding of honored dead into the structure of the central structure, and attempts to contact and control spirits from Rauh.

The Erdtree is rightly called the (most current) 'culmination of perfection', and 'Life itself'