promethean body.

Seratone:

What about a robotic/machine promethean? Or a half machine half biological construct. Is that possible?

If you ask me, an AI or robot powered by magic would probably be more relatable in a modern tale than imitating the Frankenstein monster.

I think even these ones would be affected by Life/Death magics.

And there is a Transmutation that allows a Promethean to take on the true body of a mortal for a while.  Given the fact that Disfigurements, like a Changeling's Mein, are the TRUE appearance, I would not say that Prometheans grow hair or nails, unless their body Transmutes somehow.  I got the impression from the book that Prometheans do not really change at all without Transmutations.  For example, if you are a Golem, your flesh is likely rotted and filled/covered in clays and earth.  While this might SEEM like body hair to a human, it isn't.  A Nepri is really a rotted, shrivelled mummy-corpse.  They don't really have growing hair, but their nails and teeth seem to grow larger with time as the skin rots away.  The other Promethean lineages would have the same factors.  The Unfleshed constructs and AI/Robot prometheans are even LESS likely to show physical signs of life, as their hair and nails are just artificial.

StSword:

They aren't undead, the book calls them "not quite alive" though, they aren't alive in the same sense as the rest of us though.  Like a virus, or a spirit, and yes I'm including the constructs and unfleshed in that as well.    

I like to think of them as alive in the same sense a fire is "alive", they need air to survive, they require fuel to sustain themselves, they can grow & they can reproduce after a fashion.  From the outside it has all the basic traits of a living thing, but it really isn't. 

So I'd say that, yes, their hair & nails grows naturally as a humans, might be a cute Milestone, too. "My First Haircut"

Technically no. A Unfleshed can upgrade their parts to make them taller, beefier, beautiful, whatever; but only mortals and the other supernatural would think they grown, Prometheans could tell that it was a upgrade than natural growth.

I feel that there's something missed in the discussion above (e.g. dead flesh moved by the divine fire, un-dead versus 'not alive' and spheres of magic), and that is the fact that Prometheans aspire to humanity.  As one navigates toward the end of his magnum opus, he finds himself more and more able to emulate humanity...

I dunno how it fits with rules, but I think that an affect of an especially powerful milestone being reached could be a Promethean awaking from his brief slumber and finding that he has stubble on his chin for the first time.  A muse realizes that she needs to get her hair cut for the first time, then again in a few weeks.  A Nepri who never worried about such finds himself in need of a manicurist?

...Nah, it ain't in rules, but it fits with the feel of the game, at least in so far as I see it.  I'd like to believe that most Prometheans don't have to worry about shaves and nail clippers, but a rare few might find themselves suddenly facing these challenges.  As much as I think it's a pain in the rear to have to trim my nails and get hair cuts, one of these creatures might relish the thought.

Corplos:

So I'd say that, yes, their hair & nails grows naturally as a humans, might be a cute Milestone, too. "My First Haircut"

Oops!  I didn't see that...

This is one of those situations where I'm GLAD someone beat me to it.  Of course, I'm gonna leave my post to stand.  You know, as an example of how we should read posts before posting, right?