There´s a first-level spell on the Witch's spell list avaliable for Changellings, Sow Thought, that says:
You plant an idea, concept, or suspicion in the mind of the subject. The target genuinely believes that the idea is his own, but is not required to act upon it.
I could use this spell to make someone my servant, using something like "You are my loyal servant" as the "concept" implanted?
I am aware that this spell can't directly force someone on doing something - it justs inserts a statement on the target's mind that the target will consider "true".
"I should serve that mage the best as I can" is not really different from "I should drink water" or "I prefer red-haired women", as far as I can see. The target creature will see that idea as "true" and will believe that this ideia is his own.
However, can this spell make someone believes that he/she is a servant of another person? I know that it is an unexpected use of this spell, but it seens - to me at least - fair game, considering how that spell "works".
As far as I can see, it would appears that the target will be "willing" to be a servant, but I really want some insight on how other GM's would handle this situation.
EDIT 2: Now, thanks to some awnsers, I can see that my original interpretation of this spell was kinda... off. At the moment, my interpretation changed to a "brief, passing thought". I will wait a bit before accepting an awnser.