[quote=@shylarah]
Nyx understands Yggdrasil well.  Probably a special relationship because he's Archon, though, yes?  I thought the tree itself was aware, not that it had a spirit that dwelt within it.  I am going to like that tree a great deal, I think.
[/quote]

It's both. Any sentient fae tree is capable of manifesting itself as a Hamadryad. Unlike normal dryads they are the actual embodiment of their tree rather than just dwelling there. A dryad could survive a destruction of its tree like the loss of a home, a Hamadryad would die.

Most of the truly ancient trees don't do this anymore as it leaves their trees vulnerable if they are not their to defend it. So Yggdrasil, the Borogroves etc stay within their tree bodies rather than manifesting as a Hamadryad.