There are three facts I'm not entirely sure how I want to interact in my world, and maybe typing the options out will help me (or someone can chime in with their opinions about these).
Fact 1
The magic is physical, i.e. it is a part of the physics of that world and not entirely a mystical thing as it tends to be in many fantasy worlds. As such, it is somewhat tangible and can be stored much like electricity can be (and in the case of most fleshy beings, it is - stored in the electrical impulses of their nervous system).
This is because the deities of this world are personifications of physical forces (or rather, a more or less scientific interpretation of them) and act as an innate connection between the 'mystical' and the 'physical' of this world.
Fact 2
Because of magic's tangibility, some species of creatures are capable of eating magic. The way plants convert light into metabolic energy and animals convert biomass into metabolic energy, these creatures - sirens, to be precise - convert magical energy into metabolic energy.
This is because sirens were created by a deity to be magic's natural predator, so to say.
Fact 3
Magical energy is biologically active, i.e. it retains it's magical nature even after being converted to something else, like after being consumed. It will impact the specimen like a "mutagen": should a human try to attain the power of a dragon and eat it's heart, they will find themselves covered in scales or even entirely lizard-shaped.
These "mutations" change depending on both the nature of the energy and the compatibility of the affected creature; a mermaid will have an easier time consuming a water elemental than trying to consume a fire elemental, and the part-dragon human would probably eventually die of a heatstroke due to the fire inside them.
This is the designed "cost" of doing magic and the danger associated with amassing power etc. and has been the main focus/feel of the stories I've been concocting for this world.
Now, knowing all that, here's the question I'm struggling with:
How would a siren go about gaining the ability to breathe air in this world?
She can eat magical beings to gain their powers, but that would mean she needs to find something that has a "magical nature" that includes the ability to breathe air much like the "magical nature" of a dragon includes spewing fire.
I do not currently have a creature like that.
I've been considering humans or any other land creature (or maybe an amphibian) that is magical in any way as a possible solution (i.e. victim for the siren to eat and gain their powers). But then that would mean, following my own laws of magic, that for some reason
- humans are magical altogether and the siren should just turn into a human upon eating them, which is not what I want
OR - a human's magical nature is tied to breathing air, which it wasn't so far?
OR - at the very least, the magic energy of a human is physically "stored" in the lungs (which would require the lungs to be energetically active the way the nervous system is?)
None of these feel like a solution so I'm a little stuck.
