Lore

You make it sound like that would be a tactically useful move from some perspective.
I'll stick to saying that tossing a billion clones at the milletian whenever they exit any town limits and trying to pass it off as a "We just want you DEAD" plot would be more effective than anything else.

• Fades in from nowhere* Psst, clones take resources, they aren't made from nothing. *Fades out, and doesn't come back*

The only resource(s) they're made of is magic and probably time (at least, in game). All they have to do is get 1000 (or however many to start) clones to train up medi, magic mastery as far as they can go, some other mana-giving skills, and all the music skills.
Use medi in conjunction with fantastic chorus (helps a lot, but probably not available for Cessair) and enduring melody, feed the machine for more clones and repeat until you have an army of clones capable of producing enough mana for a billion clones (or however many enough to distract and annoy the milletian, probably only need a few hundred thousand at most). The number could probably be reduced if they could teleport some back to a (ridiculously large) medical team with First Aid and Healing trained up (instead of disposing of them like I'd expect them to).

And in order to make magic, they need to kill people. The clones arent THAT easy to make.

The magic used to sustain Pincara/Nemeton needs a blood sacrifice. This cannot the same magic that makes clones.
The clones were originally supposed to be that blood sacrifice. If you're telling me the clones also need a blood sacrifice to make, then why bother making them in the first place?
I can tell you that the Clone Production Facility somewhere in Nemeton was definitely made from blood, but they have to source the magic that makes the clones from something that isn't blood (at least, not their blood).