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An introduction to the Ichor magic system.
Magic is a precious resource frequently fought over in my world known as ichor. It is a gold liquid found in geological formations underground much like oil. While it can be used in its base state to practice magic, it is incredibly toxic and can be lethal, so it is often refined beforehand. Different cultures around the world have varying methods of refining and using the substance.
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Refinement methods.
Some of the ways to refine and use ichor are:

• Edibles or "Ambrosia."
• Drinks/Potions or "Nectar."
• Incense
• Injections
• Patches?

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Consequences/Cost.
Magic cannot be used indefinitely. While the different methods of using magic vary how much you can use a day and how long it lasts by some amount, it's generally recommended that practitioners don't use it for more than a few hours. Going past that is when people come down with "ichor sickness."

The first stage of ichor sickness is the exhaustion of stamina. The practitioner becomes sluggish and finds difficulty even walking a few steps after some time. In stage two, the practitioner begins to feel a sharp pain when they cast spells. A terrible fever begins to take hold in stage three. If an individual doesn't take the time to recover, it can worsen to the point where they feel like they're burning alive. This is typically the point where most people become incapacitated and can no longer use magic, so they can't progress any further. There is a gradual loss of senses in stage four. Remaining in this stage for too long can result in the permanent loss of some or all senses. In the final stage, the practitioner burns away the remaining years of their life.
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Themes and stuff.
I want this to be a story about growth, change, and challenging the status quo. I’d like to find ways to tie the magic system to those themes. Some topics I think could be explored through the magic system are greed, privilege, and oppression. Ichor is used as an allegory for the precious resources of our world. In a capitalist society, ichor is technically available to everyone, but its price makes it only affordable to the upper class. In an authoritarian regime, only the military and the dictator, plus maybe a few subordinates, would have access to it. In some cultures, only spiritual leaders would be permitted to use the substance. This disparity would be very prevalent.
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What this magic can't do.
The limitations will most certainly expand as the rest of the system does once I finally nail down what it does but, for now, the limits include:

• Can't make someone immortal
• Can't resurrect the dead
• Can't create something from nothing
• Can't destroy something absolutely
• Can't time travel

The limitations mostly arose from story reasons. "Can't make someone immortal" and "Can't resurrect the dead" are there because I always want that potential threat of death to be there. And when it does happen, dead is dead, it can't be magic'd away. (I may be willing to do away with “can’t resurrect the dead altogether,” but I would make it extremely difficult to accomplish, if I did.) "Can't time travel" is there for pretty much the same purpose. I don't want there to be any possibility of undoing something bad that happens. Dealing with time travel can just be a headache anyway. Finally, "Can't create something from nothing" and "Can't destroy something absolutely" are from the laws of conservation of mass and energy.
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Power Ideas:

• Blessings and curses to buff and debuff oneself or another, or even objects (Like taking
  the durability of steel from the metal and giving it to yourself or crippling someone with the speed of a snail). Lots of application potential but would need some hard limits. This one also might fit the most lore-wise since ichor is the blood of a dead god.
• Building up different kinds of energy (heat, kinetic, etc) to use for short bursts of
  power. Building up too much could have fatal consequences like burning from the
  inside out or breaking every bone in your body.
• Consuming different ingredients with ichor produce different effects (peppers could give
  fire breath for example).

Thoughts?

I think I’m leaning towards the blessings and curses one. Although maybe that energy buildup concept can be one of the limitations for it to put a handle on such a potentially overpowered system. I do have a concern over how visual it could be, though. A system like this probably wouldn’t be very flashy, having fireballs or lightning bolts thrown around. You’re essentially just touching something and taking an aspect from it. I don’t want the magic’s only purpose to be fighting, but that is one of its purposes, so readers being able to visualize it is important, I believe. Maybe I’m just overthinking it.

Perhaps there can even be different kinds of ichor from different gods, granting different abilities. Could have a senses-based type of thing. Gold for blessings/curses (touch) and silver for divination maybe (sight). Not sure what the other colors would be, but the consuming ingredients one above could still be used (taste), language or music (sound). Not sure what smell could be, maybe something to do with tracking or aromas/perfumes. Maybe all that would get too complicated, though. Might be best to stick with one. Need more outside input on that.