Just a random thought...

Magic is finite, the corruption is not. The well of magic was kept full by the gods, until their death. Now that they are no longer there to refill it, it is a limited resource, and will eventually run dry. It may take 1000's of years, maybe longer, but it will run out eventually. However, the corruption is alive and self-perpetuating. As long as there is life in the world, the Blood will be there, and will be a path to power. This eventually, all magic will be corrupt, and some time thereafter the entire world will succumb to the blood.

DOOMED! DOOMED I TELL YOU!

Don't know if I actually want to use this or not, just a thought...

Notes on the nature of magic and sacrifice

Though the gods made constant war on each other, up until fairly close to the end they were surprisingly civil as to how they went about it. They chose a battleground together, and they reached a mutual agreement about many of the tools and weapons they used, such as the well of magical power that they created for their worshippers to wield against each other.

Magic is a power source. Discounting the corruption that now festers in its depths, it is value neutral. It is a source of energy that was designed to react to the will and desire of its users, and to conform easily to structure imposed from outside. Thus, rituals used by those with a firm purpose in mind will draw power from the well and cause it to shape itself into different forms.

There are those that say that magic itself has a kind of sentience, a rudimentary intelligence that responds to and communicates with those that try and use it, that consciously shapes itself in conformance with the desires of the mages wielding it. This has never been widely accepted or proven, and if true, nobody knows what effect the corruption has had on that mind.

While there is no consensus as to whether or not magic is alive in and of itself, it is clear that magic reacts to life, and is tied to life force in some way. Natural plants and animals will draw up and store a small amount of magic by themselves, and can even use it in rudimentary ways. Thus shamanistic mages have found ways to use plants and animals as intermediaries between themselves and the raw force of magic, sacrifices of plants, animals and people can give access to a sudden burst of power, and natural ingredients can aid mages in the casting of their spells.

Some shaman have found ways to use sacrifices to place a barrier between themselves and the corruption at magic's heart, or at least they believe they have. The idea is to use another person or being to cast a spell through, allow the corruption to infest that person, and kill them at the height of the spell, this gaining both an extra boost of power and a filter for the corruption and it's effects.

Some random collected notes on magic and the blood of the gods

Alchemy is a subset of Enchantment, and is a blend of magic and science, Alchemy is the safest of the magical disciplines. It's slow and methodical, skimming the top of the well, and the corruption can (generally) be effectively filtered out and avoided. Enchantment is used to create magic items and objects, including all of the techno magical stuff in the rich parts of Ammadhur.  The items you end up with can be quite powerful, but enchantment in and of itself has no direct combat or improvisational use.  Basically engineering, for all intents and purposes.  Enchanters' guilds tend to be quite politically powerful in Ammadhur.

A sorcerer who embraces the corruption and delves deeply into the Gods' blood can use it to create a variety of effects, almost anything imaginable, limited only by the skill and strength of will of the caster. However, how easy it is and the effect it has on the caster will vary depending on where the effect falls on a scale from corrupt to pure.

It can create poison, rot, darkness and corruption effects quite easily, and casters are "rewarded" (so to speak) for doing so. Fire, and mental domination are slightly more difficult. Healing and purification are nearly impossible, and would exert a terrible toll on the caster if attempted.

If performing tasks that are evil and fitting in with the corruption theme, the caster either is either unaffected or moves one step closer to "transcendence", turning into one of the more powerful and intelligent undead.   Attempting more "pure" effects brings the caster closer to death, or to transforming into a mindless undead. Willpower and discipline can slow or mitigate that change, but cannot eliminate it. Destructionor transformation are inevitable.

A direct attack that poisoned it's victim's mind and body would be a fairly straightforward use of god's blood.  Drawing someone else's strength and life force into yourself  would be more difficult, but still possible, as it has a balanced affect - harming another while benefiting yourself.  Healing wounds on another would be impossible or nearly so.  Any beneficial effect must generally be at least balanced with a harm.

Once one has physically touched a pool of gods' blood, one can draw on it from anywhere, with some limitations that I don't know yet. Merely touching it causes pain, damage and corruption, but creates the link. Immersing oneself in it entirely will either destroy one utterly, or immediately transform you into an undead.

Note that one need not eve physically touch or even see a Blood pool to draw on or utilize the Blood, or to feel its corruption. Any use of magic has a chance of opening one to the Blood, the more power used or expended the higher the chance.  However, drawing on that much power without physical contact takes a tremendous amount of magical skill and/or willpower. However, the weakest minded person, with no magical skill or training at all, can find themselves possessing tremendous power if they actually physically touch Blood.

The nature of magic.

This is best described via a somewhat extended metaphor, so bear with me on this.

Think of magical power as a well, filled with a thick  liquid that settles and gets denser and heavier as you reach further down into its depths, thinner and lighter at the surface. The denser the liquid, the more powerful the magic.  Thus, the deeper you reach into the well, the denser the material you draw up, the more difficult to lift and hold it, and consequently the more powerful the magical effects you can create. While the heavier and denser magic is more difficult to handle in terms of the strength and willpower required to use it, using it is also faster and in some ways simpler than trying to create similar effects using the lighter power towards the top. The thinner stuff at the top must be hoarded slowly over time, drawn in and pulled together with rituals and tools, with great skill and patience, to create small effects.  The stuff at the bottom is the very essence of power: draw it up, frame a purpose in your mind, hurl it away, and you can level mountains.

But, the well has been poisoned.  Magic was inextricably tied up and tangled with the gods and their power, as they created it as a tool for their vassals to use. Thus the corrupt blood of the gods, when it was spilled, infected all magical power.

The corrupt blood, to continue the metaphor, is the deepest and densest power available. Thus, the bottom of the well - the strongest magic - is pure blood and corruption, and the corruption gets lighter and more sparse as one rises up to into the lighter and clearer power. However that corruption is not limited strictly to the bottom, some will always diffuse upwards.  Any use of magic has at least a small chance of touching on that corruption.

There are ways of doing magic that are very safe, if never perfectly safe.  Alchemy and enchantment, by working slowly and carefully, accumulate small amounts of power slowly, skimming the very top of the well over a long period of time, and minimizing the chance of corruption. Alchemists will say that their works are completely safe, but of course there is always some risk, however small. With great skill, and great patience, wonderful works may be created this way, with minimum risk, albeit slowly.

There are  pools and rains of Blood that are physical manifestations of the metaphysical bottom of that well of power.  That power is so great and so dense that it has an actual physical presence, manifesting in the physical world even when not being actively used. 

It is technically possible to be a classical D&D style sorcerer, without touching the blood. But it requires tremendous skill and not a little luck.  One must be deft in drawing power from the well, knowing how deep one may reach and avoiding the wisps of corruption that reach upwards.  Some succeed and attain power without risk.  However most such practitioners eventually pay for their daring.  It is difficult to sense the Blood if you have not already been corrupted, and thus it is very difficult to avoid those thin wisps of Blood that rise up through the well for very long.

The metaphor of the well is so widespread that those who fall to the blood have long been said to have "drawn too deep". The phrase has been generalized over time, and now anyone who does something foolish and dangerous or self-destructive is said to be "drawing too deeply", "diving" or "swimming in it".

I want one thing to be completely clear:  once one touches the Blood, even the tiniest amount for the briefest time, corruption is inevitable.  That person is, in one sense or another, doomed, without any recourse and without any hope of redemption.  The corruption can, with skill and willpower, be held back and repressed for a time, the process slowed, but it cannot be entirely stopped. The most one can do is hope to die by other means before the corruption kills them, as any other death they may have will surely be a kindness compared to the end that the Blood will give them.  The effects of the Blood cannot be cured or undone.

Of course, the mage who finds that she has touched the Blood, be it accidentally or deliberately, with their hands or even just with their minds, does in fact have  a choice as to how to face the consequences.  She can fight the corruption, or she can embrace it.

The Mage who chooses to fight the inevitable will die, disfigured and mad, and in horrible pain. All she can do is delay the inevitable.  She can try and ignore it completely, or try to fight the corruption, and either way she will descend - quickly or slowly, but inevitably - into madness and eventual death.  Ignore it or fight it, the result will be the same in the end, though with willpower and self control, the descent may be slowed. 

On the other hand, she may bow to the inevitable, embrace the corruption, use it consciously and deliberately, and she will transform eventually into one of the intelligent undead, the "Blessed".