It would be rude to stomp around the top of the Tree without talking to the tree herself, I'm pretty sure, so I've spent a fair amount of time with Yggdrasil herself along with Vidopnir. She's not precisely chatty being, you know, a tree. But she's more than just a symbol, too.
So the whole point of dragon/phoenix work is ascension. Not strictly in the sense of going up, because obviously serpents like to hang out underground and all, but becoming more than you started out as. But in terms of unfolding the origami, in terms of getting where we want to go, she can walk us through the path.
It's not just a pretty metaphor to say that the eagle sits at the top of the tree and the serpent sits below. She is an essential part of the work, and an active one, if you let her be. She's the tree of lives, connecting the worlds, passing out fruit (apples, peaches, pomegranates). And the overlapping energywork... the sephiroth (there's one pair), interpretation of the chakra (there's another pair) are expressions of related things. (That takes me back to rainbowland and to some of the shit I was doing in college...)
The phoenix burns itself. The work is internal destruction, rebuilding the self. Nidhogg chews on her roots. The dragon's work is external - tear down the established order, lay the groundwork for the new.
Of course they're in opposition - and there's no shortage of stories about the opposition of thunder and scale, really - and she, the Tree, she is the liminal space between inner and outer self as much as she's the liminal space between worlds. She is the one who connects the dragon and the phoenix, the serpent and the eagle, the inner and the outer worlds.
Peace between within and without isn't easy. But it's necessary if you're going to get beyond the Tree. She is patience, and she is stability. She'll outlast her inhabitants, I don't doubt, even if things look pretty bad right now.
She asks for sacrifice. She wants to know that those she teaches are serious, are willing to put the work in. I think that's fair. She demands honesty with myself, with my partner, with my life. That's intimidating, too.
She sees everything. Her roots rest in Mimir's well. She shelters the Norns. Gaining her wisdom means accepting that some things cannot be changed. I look at Odin, who knew exactly what was going to happen to his son. Did he think it was worth it? Did it matter?
I guess it depends on whether I believe wyrd is malleable or not. If it's not, then the choice is simply between the illusion of freedom or knowledge. If it is, then choosing not to accept it is a valid choice.
She teaches me that it's okay to be tamed. This is a lesson I fought for a long time, but it's very relevant to my life now.