If you are using a Nacreous Gray Sphere (Flawed) Ioun Stone you always look the age you were when you first used it.
What happens if your appearance changes drastically afterwards? Will those changes be incorporated into the way the stone makes you look? It only speaks about age.
1: Scarring
2: Reincarnation into a gnoll
3: A changeling becoming a hag
4: A sex change item
If a 16 year old changeling girl finds such a stone and at age 26 she is afflicted by one of the above, does she still look like her 16 year old self or does she look like a 16 year old
1: but scarred
2: gnoll
3: hag
4: boy
or does the stone treat her as a new wearer for 2-4, fixing the immage of a 26 year old of her new looks?
As you said tourself, the stone only refers to age. Any changes changes other than ageing would not be affected by the stone.
In all of these cases, it's the same creature. The ioun stone remembers the age of the creature the first time they wear it.
1. 16-year-old changeling with a scar.
2. 16-year-old gnoll.
3. 16-year-old hag.
4. 16-year-old boy.
It's pretty straightforward, really.
A lot of things that have "no mechanical effect" ending up having pretty extreme mechanical effects in the course of playing out the narrative effects. For example, having a visible scar in one area of my on-again/off-again homebrew campaign would get you banished or executed. Doesn't get much more mechanical than that.
It's a bit simpler if we use the definition of age that talks about development rather than years since you were born. I feel that this definition makes more sense given the age category references in the better versions of this stone.
Looked at that way, you'd appear to be a creature of the same age category if you became a different creature.
1. 16 year old Changeling with a scar
2. 9-19 year old gnoll
3. There's no way of knowing. The ritual to turn into a hag and the description of the effect are both unwritten. If an effect of the ritual is to unnaturally age you, then that part wouldn't happen.
4. 16 year old boy
A lot of things that have "no mechanical effect" ending up having pretty extreme mechanical effects in the course of playing out the narrative effects. For example, having a visible scar in one area of my on-again/off-again homebrew campaign would get you banished or executed. Doesn't get much more mechanical than that.and how does your home game apply to rules or RAW?... it does illustrate that home game GMs customize their games.
sure, there are narrative and story things but when they cross the line into bonuses THEN they have an effect or impact. In this case wearing the item all the time negates any possible crcm bonuses...
Narrative examples are by definition "home game", but that doesn't make them any less applicable. There's more to rules, including RAW, than mere numbers. Knowing how an effect plays out in both qualitative and quantitative ways can have a drastic effect on a character's narrative experience. There are absolutely situations where having a visible scar will affect the game.