My mind was screaming "Revisions! Revisions!" last night and is still screaming that, so the post today's going to be short, sweet, and hopefully inspirational.*
Fact: Possessing a piece of someone's body gives you power over them. Hair, skin, teeth, organs, blood, doesn't matter what—you can still control them with it.
Fact: DNA is the most fundamental part of our bodies. It decides what we look like, how we work, what diseases we'll get, and probably some parts of how we act.
Fact: We are capable of replicating DNA in a laboratory.
Fact: Anything that can be done for good can also be done for evil or profit (or evil profit).
Idea: It should be possible to take DNA samples from unsuspecting people, use replication techniques to get a usable sample, and then use that sample for black magic.
Idea: It is possible that blood, gamete, and organ banks (etc.) sell to practitioners of black magic on the side.
Idea: If DNA determines magical signature, it could be possible to frame someone by using a large DNA sample as the power source in a spell. A stem cell culture would work nicely.
* In my defense, I have ten pages left until the end of the manuscript this time around. However, I have no idea how long that'll take me to get through, since part of the revisions is expansion.