Arcanists and their spells

[Alenore]

I've seen it like "I manipulate the aether flow in such a way you're deprived of it, so you fall sick since that's pretty much what makes you stay alive".

[TinyRedLeaf]

I always assumed that just like they search for the formulae that represent matter, they also search for formulae to tear it apart.

That's basically how I've always approached arcanima as well.

Arcanima, as described in the lore, originated in the Southern Islands, presumably among the native lalafell communities. I imagine that the art grew out of the calculations necessary for blue-water navigation. Anyone familiar with sailing would know, for example, the importance of being able to calculate latitude and longtitude to navigate a landscape with no other landmark.

Arcanima basically describes a scientific, mathemathical approach to invoking magic (Mahouka, anyone?). Or, to put it another way, it's about manipulating aether with maths to fuel physical phenomena. Which is why you'd notice that none of its spells has any relation to the elements, unlike black and white magic.

Now, one way to use arcanima is to heal disease. Biological sickness is caused by various physical agents that can be ameliorated by arcanima, if not outright eliminated. It's a simple matter then, for a skilled arcanist to reverse that process, to inflict the same physical phenomena that cause disease, and hence injure or kill an enemy.