What does the dragon want?

[Quertus]

Having actors move without motivation and having to retrofit a personality to create a motivation, with a side of Mother of Dragons may I derivative feel? If I didn't have a headache, I think I'd be getting a headache.

But fine. Not that I've explored similar mechanics (cool idea, btw), but, if such a Dragon existed in my worlds, what might its motivation be in attracting the PCs? Hmmm...

Its true motivation is likely different from its presented motivation. Its true motivation may be simple, like that it is bored, or complex, like having humans walk its slopes will change the spirit geopolitical landscape in a way that favors its long-term goals (it may even nudge "random" encounters towards or away from the party to encourage such an outcome). Or it may be interested in "is that a dragon in your pocket, or are you just happy to see me?". More on that later.

Its... "presentation" could play up haughty dragon, ancient sage, nature spirit, or (incongruous with calling them there in the first place) loner hermit. Or it could do something silly, like acting like a person being walked on during a massage "just a little to the left - ah, that's the spot". But such presentation is likely in service of its goals (actual or presented).

Its presented motivation is likely something simple, basic. Something the PCs wouldn't question. Before choosing it, decide whether it wants one that brings the PCs back, or encourages them to stay away afterwards. Whether it needs more out of them, or wants to limit interactions to limit questions and the likelihood that they'll see through the facade. And whether that itself is truth of facade.

Its presented motivation may be a simple quest: this thing is annoying me (negative), this thing I want (positive). It may be "important": I have a goal (positive) or regret (negative) I can't attend to. Note: it may or may not want to reveal its weakness in being "mountain-bound", or the exact nature of the social dynamic with the other spirits. But, OOC, it's too cool not to tell the players at least one half of that, so you've got to figure out what it will say, why, and how.

Or... it could serve as an info-dump. But retrofitting an info-dump is kinda dark side.

As others have mentioned, ancient beings do often have regrets they might want to deal with. And allies to present tokens to. But I think the one most appropriate to the party, and to a mountain dragon, and to an ancient being would be for the dragon to care about its offspring, for it to want the party to deliver a petrified egg to an energy source, to awaken it. Perhaps this dragon wants to give its children a head start (what parent doesn't?), and has spent the last <very long time> crafting a special McGuffin, to harness a *new* energy source (sunlight, time, grass (darn Pokemon elements), magnetism, rainbows, gravity, whatever), and wants the party to deliver the egg + contraption to someone who lives at a "conflux" of the element. Note that the existence of such a conflux could be an "info dump", and revealing it could be part of the dragon's plan.

Now, its actual goal may be to get the party to awaken their dragon, or get them to research building their own McGuffin / ask what other kinds of dragons might be made, or even get the party indebted to it for its help with creating such a McGuffin. Or their egg might be the child of a friend (or enemy), that it wants to exert influence over, or even the perfect friend/companion/minion/mate for its own child that it just sent off to be hatched. Or just to interact with the ally/conflux. It depends on the dragon (and the nature of being pseudo-elemental) as to how sane and how likely to be achieved its goals really are.

Or its real goal could just be that it's bored, and all this is just a distraction, that the party can see as many (or as few) layers in as they want, and still see something reasonable rather than just a tired old mountain wanting a few words and a free back massage.

But what its motivation is will (or should) change its responses and delivery, what alternatives it will consider and why, so it makes for a more consistent and believable experience to figure such things out before you introduce the actor to the stage.