Hereditary Change spell
 

As it says. The spell makes an advantage, disadvantage or feature hereditary. The subject must first have the quality to be passed down. The spell costs 100 energy times the point cost of the quality, to a minimum of 100 for zero point features. At the GM’s option, this spell can also be applied to such attributes as hair or eye colour.

This is a Body Control spell, and has Alter Body for a prerequisite.

Obviously this is just the first draft. Feedback and commentary sought. I’m considering a variant that allows mental qualities to be made inheritable.

Re: Hereditary Change spell
 

It's a worldbuilding spell that is probably harmless on the time frame of a typical RPG but would be setting-breaking on a time frame of tens of generations.

Re: Hereditary Change spell
 

Well, yes. It’s magical genetic engineering, the implications are fairly obvious. The nobility/aristocracy/elite could be genuinely superior, provably and measurably. Cattle could be improved, as could crops. On a darker note, it would be possible to breed populations who are naturally inclined to good looks, strong libidos and profoundly submissive temperament.

I’m mostly looking for feedback and suggestions concerning the mechanics.

Re: Hereditary Change spell
 

In case you're not aware of it, page on 32 of Biotech there is a spell, called Spellgraft, to give an unborn child a spell as a "racially innate spell", (B453).
Effectively, it's enchanting the fetus.

Re: Hereditary Change spell
 

"must first have the quality", well, many qualities are [already] hereditary, so this cuts into the utility of the spell a lot. Which is probably good from the standpoint of it not being too destructive to your setting.

Hereditary doesn't mean all your offspring have it. If it does, then it has to be sorting which of your chromosomes are getting passed on, which means they will be more alike than most siblings in other ways too, your fertility will be reduced (half the offspring you "might" have had vanish after all) and/or that using the spell to pass on multiple qualities might be impossible, or at least fail half the time.

fixing hair or eye color also raises the issue of what happens when you inherit different fixed traits from each parent. It's possible this spell means you cannot have offspring with someone else enchanted with this effect. Which will badly cut into its utility in creating a genetic aristocracy.

Re: Hereditary Change spell
 

You might want to limit the spell to physical and mental traits. Imagine the chaos/paradox when the emperor's 100 children all inherit his rank.

Re: Hereditary Change spell
 

When you look at what Greater Wish does in game mechanics, this spell seems to accomplish similar end results: the ability to add or subtract traits.

As others have pointed out, genetics doesn't quite work the way this spell description would make it seem to function. If what this spell effectively allows is genetic manipulation, using Biotech in conjunction with magic may be the way to go. The real question should be: what are the side effects, genetically speaking, of tampering with the genetics of a living creature? What if the reality is, two genetic "tweaks" end up imposing abnormal genetic combinations that result in disadvantages? What if, the alterations produce an entire new species unable to reproduce save with others of its own modified template (ie, the magic turns one individual from a donkey into a mule where the chromosome counts make the subject of this spell into a form of hybrid?

Any spell you introduce into your campaign is fine - it is, after all, your campaign. 😊

My comment is geared towards say, A player in my campaigns who proposes a spell that is potentially cheaper than a spell that already achieves essentially the same effect (aka Great Wish)

Re: Hereditary Change spell
 

There's a difference between Musical Talent or Intuitive Mathematician running in a family and every descendant of an individual having specific traits.

The advantage of marrying the heir to someone who will guarantee strong advantages to all future heirs to the estate is powerful. Over time the high nobility would become amazing. It could explain the origin of elves in many worlds.

Re: Hereditary Change spell
 

There'd be several possible ways for it to work.
It might always be passed down, which as other people have said might produce strange complications. Possibly, if there was no limit on it then after a certain number of generations the whole population would have it.
Or it might be a dominant trait, in which case all the subject's children would have it but their children would have a 50/50 chance of having it (if none of them married people who had the trait themselves).
Or it might be a recessive trait, in which case none of the subject's children would have it (unless the subject married someone who also had the trait) but they would carry the gene and if their children married someone who also had the gene their children might have it.
Or it might be that having two copies produces the full effect and having one only produces half the effect, in which case the subject's children would all have lesser versions of it.

Is this meant to be used to make traits added using Alter Body and similar hereditary? It seems like, if so it might still be useful even if it just worked like it would if they were normal traits and it would also raise the possibility of people adding traits that the species wouldn't normally have.

Possibly, different worldbuilding results might be produced depending on whether you had it work straightforwardly by GURPS traits with no other complications or whether you had it work unpredictably like real genetics - for instance, it might be that a particular royal family that's been favouring a particular trait for generations is now cursed with some disease that they hadn't realised that the same gene was a risk factor for (and possibly still don't), or it might be that another has been favouring a particular trait that's actually the one-copy version of something and the two-copy version, which one in four children of two one-copy people will have, is something much more unfortunate - you could get some quite strange populations that way without them or their neighbours necessarily realising why they were like that.

Re: Hereditary Change spell
 

That is the intent, yes.