We've been told that mind-altering spells wear-off fairly quickly, but there are a few possibilities that would skirt that issue and a few mysteries that need to be cleared up.
First, the questions.
1: Are living beings the only thing capable of crafting and powering magic, or is it possible for magic to power itself from some other source.
2: We know magic can transform matter, but can it create it?
3: Can magic only work as spells, or can it be expressed as an effect of a person? Is mood hair an uncontrolled expression of magic, direction of a spell that was invoked long ago, or is it a force-of-will thing?
4: What ARE the restrictions on resurrection? I would assume that the brain must be intact and fresh, but is that all?
5: Since spells are 'bookmarks' it begs the question: Is there any way to teach somebody a specific spell? How about to transfer a cast spell to another person?
6: Do runes and symbols have any specific value? Do they modify and shape magic in predetermined ways, or are they simply an alternate means of 'bookmarking' and recalling a spell?
7: Is it possible for a strong caster to take control of a weak caster's power?
The reason given why Mary is eating people was implied to be either Pavlovian response or the result of physically altering her brain, but that's hardly
A few overlooked ways to cause and sustain Mary's bloodlust:
Number 1: Chemical stimulation. Craft a spell that dumps aggression and hunger inducing chems into the bloodstream. Since it wouldn't be working on the mind it would last as long as any other spell. If you implanted the person with extra glands to
produce those chemicals then all the magic would need to do is keep the chems contained until it's time to release them, at which point the person would be faced with overwhelming urges to kill and eat.
Number 2: LAND attack. Distort the person's own magical ability to your own ends. Instead of casting a spell to cause a bloodlust, force the person's own magical power to induce the bloodlust. Since they're constantly regenerating the spell it would never fade on it's own.
Number 3: Have the spell power itself from some other source, such as the lives/blood/etc of other humans or environmental magic sources.
Number 4: Misdirection. Mary's spell is being re-cast regularly by the thin man, but she is not aware of it.
I'll add to this list as I think more possibilities up, but for now can we just start flinging wild conjecture around in the hopes of hitting something awesome?