Pathfinder: Construct tattoos.

[Calthropstu]

A tattoo mage has had a homonculus crafted in my game and seems to think he should be able to tattoo on his homunculus. Barring actually tattoing, he wants to circumvent the obvious difficulties by simply tattooing himself then using the transfer tattoo spell to move it to his homunculus. He is quite adamant that he should be able to do this.

I have several misgivings regarding this. For one, tattoo spells state it must be done into flesh, and the homonculus is not made of flesh.

For second, clay doesn't seem like it could hold ink tattoos properly. The process for painting clay and for making tattoos is completely different.

Third, if he uses it the way I fear, it will be a 13th combatant to track. Our combats already take hours. Today I had to work 26 npcs on the map.

So, how would you guys rule it? I gave it to him temporarily, and said I'd research it for next session. Figured I'd ask here and move on from there.

[Ashtagon]

You have a number of options:

1) It's magic. It just... works.
2) Because the "skin" is not viable to hold a tattoo, you could rule that the tattoo fades after a week (or sooner if actively washed off by cleansing agents or environment), at which point that tattoo is lost forever. Note that this effectively means making on-the-fly rulings for a great many creature types (and also effectively bans tattoos for warforged PCs).
3) The tattoo arrives on the creature and remains magic, but because it's not on "flesh", it can't function or be activated. Again, this may require on-the-fly rulings by skin type.
4) You could rule that it can work on constructs normally, but not on a homunculus because that is essentially an extension of its creator's own soul. If you do this, you should probably allow for some kind of "share tattoo" ability, similar to how familiars works.
5) Something else.

[Calthropstu]

You have a number of options:

1) It's magic. It just... works.
2) Because the "skin" is not viable to hold a tattoo, you could rule that the tattoo fades after a week (or sooner if actively washed off by cleansing agents or environment), at which point that tattoo is lost forever. Note that this effectively means making on-the-fly rulings for a great many creature types (and also effectively bans tattoos for warforged PCs).
3) The tattoo arrives on the creature and remains magic, but because it's not on "flesh", it can't function or be activated. Again, this may require on-the-fly rulings by skin type.
4) You could rule that it can work on constructs normally, but not on a homunculus because that is essentially an extension of its creator's own soul. If you do this, you should probably allow for some kind of "share tattoo" ability, similar to how familiars works.
5) Something else.

Won't work on golems regardless because magic immunity.
There is ambiguity in the spell he is using as well as the base for tattoo magic in general. There is wording that implies the recipient must be living (which a homonculus isn't) but it doesn't explicitly SAY it except if you transfer a tattoo from a dead creature it can be transferred to a living one.
Tattoo magic itself claims it must be done "on flesh."
Another person in the group tried to argue "the homonculus does have flesh... its flesh is made of clay." Kinda a stretch and not buying it.

My main worry is action economy at this point. If I give him this, he uses his 1/3 cost tattoo scrolls to set his homonculus up as a utility caster.
To be fair, they have had to grind every step of the way, and it is getting to the point where the enemies can one shot some of the weaker npcs.
Maybe I should let him have it just because of the sheer number of times I have killed their characters and cohorts and allies. The AP I am running is brutal.

[icefractal]

Too many combatants can definitely be a problem, but I don't think this would be a big contributor to that. Even 1/3 cost scrolls are usually not practical to use every round in combat, and the homunculus could already use a wand.

How's the party that big anyway? Lots of players, or do a lot of people have minions? You might want to set a "one active extra per PC" limit, whether that extra is a cohort, eidolon, homunculus, animal, or whatever. You should let people rebuild if so, of course.