So I'm in the midst of writing a VA fanfiction and was thinking about some stuff about compulsion, and I had a bit of an epiphany.
All Moroi have a low level of control over the four elements (air, earth, fire, water) until one of their abilities spike, and they call that specialising. People who specialise in spirit where originally considered to have not specialised at all, because while they had a higher than average control over all elements, none of them spiked. Additionally, all Moroi have some ability to do compulsion, with some being better at it than others, and spirit users are particularly good at it.
So here's my theory:
What if all Moroi have some control over all five elements (air, earth, fire, water and spirit), but only the rare few specialise in spirit.
Being extremely good at compulsion is considered a marker for spirit-users, so what if that's their 'spike' in their particular element? When they specialise in spirit their compulsion ability increases too (we don't know if Lissa's ability to use very strong compulsion was always there, or if it only developed along with her other abilities after the car crash. This theory suggests it was the latter). Meanwhile, those who specialised in a different element still retain a small control over all elements, including their ability to use a bit of compulsion/spirit.
Okay, so I was really excited when I thought of this, because it fits really well and it also explains why spirit users are particularly good at compulsion and why Lissa and Adrian couldn't use it when they were on the medication (anti-depresants and bi-polar medication) that cut them off from all their other spirit abilities.
EXCEPT....
Strigoi can use compulsion too. It doesn't come up very often, and Richelle Mead seemed to mostly forget about it after Frostbite, but when Rose and the others are held hostage in Spokane, Isaiah uses compulsion on Eddie. Rose even says that Lissa wouldn't have been able to use compulsion that strong (although we find out later that she can when she uses 'supercompulsion' on Jesse).
This ability completely contradicts what would have otherwise been a very neat theory, as it is well established that Strigoi and magic don't mix. Magic is living and Strigoi are dead, and that's why magic wards keep them out and charmed stakes kill them. Additionally, the books theorise that while the power of the main four elements is taken from the physical world, the power behind spirit comes from the user's own soul or essence. That's why they can do such powerful things that can't be physically seen or felt in the same way as the other magic (compulsion, healing, auras, dream-walking, etc vs creating fire or manipulating water), and it's also why spirit users go insane; they have to give a part of themselves (their souls, their sanity) to create their magic. But Strigoi don't have souls (or they're not connected to them anymore), therefore they can't draw from them in order to use compulsion. Which means that compulsion isn't a fundamental part of spirit, it's simply boosted by it.
So yeah, I'd love to hear what everyone thinks of this. Do you think that my original theory might be correct and that there's some other explanation for why Strigoi can do compulsion? Or is compulsion just something unrelated to (though enhanced by) spirit but that everyone can use? If anyone has any other theories or something to add, then I'd love to hear it :)