Build-A-Magic

[CidtheKid]

On the other hand, making it permament could have some interesting ideas to it. If its permanent, then it probly remains in the body, which you could then extract upon the users most likely incredibly violent death. Or extract through other means or whatnot. It could become much more expensive, and then you have the whole "only rich people can afford it" coupled with "you can get it by killing people" combo that guarantees plenty of conflict.

Keep the power levels at nothing too big, make getting more power addicting, and you have something pretty cool going on.

[Herzinth]

Make it into a pill. Say if you want to be a wizard, Harry, take twice daily for the rest of your life. If you stop the pills, your magic will fade and you can never do it again.

That could work for the future, but most of the stories will probably be taking place in the normal kind of Dark Ages era of the world.
Pills don't really fit into the Dark Ages.

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On the other hand, making it permament could have some interesting ideas to it. If its permanent, then it probly remains in the body, which you could then extract upon the users most likely incredibly violent death. Or extract through other means or whatnot. It could become much more expensive, and then you have the whole "only rich people can afford it" coupled with "you can get it by killing people" combo that guarantees plenty of conflict.

Keep the power levels at nothing too big, make getting more power addicting, and you have something pretty cool going on.

Hmm. It could be stored in their blood, as it were. So by collecting and purifying the blood of a mage, you get the magic.

[CidtheKid]

Hmm. It could be stored in their blood, as it were. So by collecting and purifying the blood of a mage, you get the magic.

Sure, but lets not make it so drinking it gives you powers.

That has bad things going on.

Now, Mage Blood destilation. Thats something to look forward to. Alchemists would've killed to be able to legitly do that sort of thing.

[Herzinth]

Sure, but lets not make it so drinking it gives you powers.

That reminds me... one of the stories I wrote (which was actually about the afterlife as opposed to this world, but w.e) involved drinking peoples blood in order to survive. Wheeee.

[Herzinth]

Also, could you explain why your against the drinking of blood idea? I mean, if it's stored in the blood, why wouldn't that work?

[Azarthes]

MY LITTLE DRUG ADDICTION
MAGIC IS MAGIC

[AngelKitten]

If using it caused the magic to solidify in the environment (such as in your hypothetical battle scene) wouldn't someone just keep using it and eating it again to have a constant supply without the need to seek more? Just a thought.

[Herzinth]

If using it caused the magic to solidify in the environment (such as in your hypothetical battle scene) wouldn't someone just keep using it and eating it again to have a constant supply without the need to seek more? Just a thought.

It would take awhile for it to coalesce. Perhaps a week or so? Depends on the concentration.

[AngelKitten]

It would take awhile for it to coalesce. Perhaps a week or so? Depends on the concentration.

In theory someone could still wait the amount of time and collect it, unless they used it faster than they could ingest it again. Unless they had to constantly be on the run because they were in danger of being killed or something.

[Jorick]

You might want to consider is the source of this magical power before these specific questions, because the source could give you all the answers. Is it truly just a natural occurrence or was there some cause behind the liquid/crystals coming into existence?

One thing you could use to flesh out the mythos of your world is that this stuff is essentially the blood of the gods. There was some major war between them in the distant past, well before the time of recorded history of your world (or there could be some recent ones) and their shed blood is this magical liquid that crystallizes under certain circumstances, maybe only if the god was very powerful and there's a high enough amount of the blood in one area that the ambient power radiating off of it can cause the transmutation from liquid to crystal (or if there are more recent god wars it could be a time-based thing, takes a few decades/centuries to crystallize). This stuff being god blood would give a logical basis for why it gives magic powers, why it's stored in the blood of human users, and why there is no loss of net power in consumption and use, why using magic leaves tons of power in either liquid pool form or in ambient form like steam/mist; gods are technically eternal, only able to be destroyed by other eternal beings, thus human use is just funneling the power through them rather than truly consuming it. Minor and moderate magic use could only leave behind the vapor form of the substance and thus give humans the impression that the power is almost wholly consumed when used, such that only extravagant uses of magic leave behind enough to form pools of the substance. This sort of thing, having it act kind of like water, could open things up like having extremely sensitive magic users able to find and absorb clouds of ambient energy or maybe some magitech created by rich people that can suck up such clouds and condense them into the liquid form.

I went a little more in depth there than I intended, oh well. Anyway, if you use the god blood idea, I'd say that mixing it with other things probably wouldn't do anything and there's no way to make more of it short of wounding a god, if there are any left at all. Temporary power that passes through the system. Its physical characteristics should be fitting with however you set up the gods of your world: rough and foul if your gods were awful things, nice and shiny and stuff if they were typical good guy gods, perhaps it depends on which god it came from. That'd allow you to have different levels of power and different things that are allowed or maybe just preferred depending on which blood you're using: a god of peace's blood would suck for/be unable to do war stuff but could do all sorts of non-combat things, a god of war's blood would be the opposite. Or if you want it all homogenous then it would be limited by what the gods themselves could do, perhaps allow humans to have ~5% of their power level when using their blood, the exact applications of the power being limited by imagination only.

Or if you want to go with it being a natural resource of the world you just have to be sort of logical with it. What environments does it appear in? Underground, forests, lakes, etc. To make it less accessible and more a rich person resource, perhaps take a page out of Dragon Age's book and make it a thing that has to be mined from deep underground and thus is not something you can just easily find somewhere. After deciding how it's found you can decide kind of whatever you want for those questions you asked. Could be temporary power by way of, for example, having the substance just sit in your stomach (hey, organic limitation on power cap there, you can only have as much as you can fit in your gut) or have it digested and float around in your blood and you burn it off as you use it, just the same way as you use up various minerals and things in your body as you exercise. Could be permanent power increase by way of having the substance be inside your body permanently and your power limitation is physical or mental exhaustion rather than a legit depletion of resources. A natural source should of course be able to be combined with things, and if it's a metal you could do all sorts of shit like making magical alloys for weapons and armor. What exactly it does when combined with stuff is up to you though, as the possibilities are limitless. Going the natural resource route is kind of the "I'll do whatever the fuck I want with magic" route because you set all of the boundaries, anything is potentially logical because you're making it all up as you please, whereas having a supernatural source would have some logical limitations that you should follow for consistency and such (divine power shouldn't be able to mix with mundane things and be improved, for example, because that would only pollute the divinity).

I dunno if any of that was helpful, but those were the ideas I had upon reading the OP.

EDIT: I just saw your question about blood drinking. It's a potentially lame idea because everyone would of course be like "lolvampires," but it could also work if you want it to. Reason for it not to work would be that the power is so evenly spread about the body that you wouldn't really get a justifiable amount of power from it unless you literally drain them dry or they were just fucking loaded with power. Or it could be that the second round of going through a human digestion tract diminishes the power such that it's just a waste. However, you could have it work just fine if you wanna use the blood drinking power thief idea, it's your story after all. Or if you use a permanent power acquisition idea rather than temporary storage you could have them kill people to steal the substance, rip out their stomach or whatever. Fun times.