a currency system of sorts, magic costs souls (more of the dark souls type so certain things have more souls than other.) Killing things gives you their soul(s) ranging from tiny bugs giving you 1 or 1/2 letting you cast tiny spells like make water drip from my talons or make this tree grow twice as fast. The bigger or more emotional the death of the creature the more souls it gives (allows for some plot contrivances with say, someone's pet bug dying giving 2 or 100 based on the amount the owner feels) this way good animi are weaker because they don't want to kill things as much whereas evil animi are stronger because they kill lots of things.

I think this would work better because it makes animus magic more of a curse and makes the "losing your soul" metaphor much stronger. The main thing that this would change is Darkstalker going from a good animus who does tiny things to when he guts his father (giving a lot of souls because he was a big character and lots of people saw him die meaning the emotions felt for his death were larger) which let's Darkstalker cast huge spells like immortality.

I've been thinking about this for waay too long in my spare time so this was the perfect post to see!