How to fight an Eldritch Abomination

Question

The Situation

The fantasy world of Terrearth is once again threatened by the Shadow, a sentient, but completely unintelligible being composed of Absolute Evil, whose sole purpose is to destroy the world to replace it with a plain of absolute nothingness, in which evil will be the only thing left. The evil will have a physical form in this world, and will be the only thing that will flutter over it forever. However, at any era in which the Shadow occurred, a group of heroes managed to banish the being in an underworld, but they have never defeated it definitively. Now, the Shadow has come back, and the inhabitants of Terrearth do not know how to deal with it. The knowledge of how the heroes of the past times defeated the Shadow are shrouded in a cloak of legend, and therefore it is the duty of the armies of the lands of Terrearth at least to try to limit the Shadow, awaiting the arrival of the heroes.

So, how can humans deal with this cosmic horror? I'm not looking for a way to defeat it permanently (because I know what is), but a way in which "simple" human beings may be able to fight it and contain it.

Humans Background

• Terreath universe is a fantasy world, populated only by humans and supernatural entities like ghosts, lich, ent and monstrous animals. There are no other sentient races apart from humans.
• Technological level is medieval. There is no gunpowder, however alchemy is quite advanced, and allows you to have healing poultice and body booster similar to our combat drugs.
• The magic exists, but is not widely practiced, as it is difficult to understand, and there are no institutions or groups of magicians dedicated to the research and understanding of it.
• The few holders of magical power are druids. These figures are priests scattered in some forest villages, who are dedicated to the study of natural and healing magic, and hand down their knowledge to their children. Druids form a social entity called the "Circle", but it has no political or religious power, and it is only a way to exchange information and knowledge during meetings.
• There are no gods or goddesses, and there are no forms of organized religion. All the inhabitants of Terrearth however believe in one principle, the Good. The Principle of Good is universally accepted by all.
• There are not clerics. There are paladins, who fight evil, but there is no religious figures assimilable to organized religion figures.
• If we should make comparison with D&D Alignment system, every people of Terrearth would be Lawful Good. In the world of Terrearth most evil does not exist. There are no wars, genocide, torture, etc. Some minor crimes exist, but put in place by those who have a relativistic vision of the good. Few are the people who belong to the alignment Neutral Good and Chaotic Good, and are viewed with suspicion by Lawful. In addition there is a nomadic people, whose relationship with other people is quite tense, whose allinamento oscillates between Chaotic Good and Chaotic Neutral.
• There are many countries, but the armies are mainly used to fight crime and the Shadow.

The Shadow Background

• The Shadow is all the evil that man can provoke, and tries to take in the world, not with violent and bloody hordes of his minions, but infiltrating, acting slowly and without emotion.
• The Shadow flourishes in living corroupting them and bringing out the dark side of man. A corrupt man will dedicate himself only to evil actions, paving the way for other infections. However the corrupt do not openly expresses his evil acts. He prefers to work stealthily, and when the opportunity to spread even more evil is ripe, he acts.
• After the Shadow infects all living in an area , the whole area becomes nothing. The only thing there is a dense and impenetrable cloak of pure darkness, which is the physical form of evil.
• The Shadow sometimes manages to create minions made of absolute evil, but they may last only a few days before fading. The Shadow prefer to resort to corruption rather than the creation of minions.
• Human armies have managed to contain the Shadow after it has eaten a large territory on the northern edge of the world, however the Shadow infiltrates more and more human in the ranks.

EDIT The magic is difficult to apply because the only types of magic "socially acceptable are elemental and healing ones, and the only holders of these knowledge are druids, pretty jealous of their knowledge. The mental and arcane magic is opposed and seen as unhelpful. Since no one is devoted to its study and most of the few magicians who master this type of magic are self-taught, this type of magic is not widespread.

EDIT 2

The reason for there is an almost monolithic belief system is historical. Before the advent of the Shadow, the world was more or less like ours. Wars, conspiracies and evil spread. In short, there was a gray morality. When the Shadow had appeared for the first time in the world, Terrearth risked being destroyed just because the Shadow attacked aggressively, taking advantage of all the evil available at the time. Some heroes managed to banish it, and the world returned to the usual evil. When the Shadow came for the second time, and was bannished for a second time, the people realized that the Shadow needed evil for his purposes , and established the Principle of Good. Now, it is true that there are different philosophies about the Good (Lawful, Neutral and Chaotic). There is also this nomadic people who while not indulging in evil acts without reason, give no importance to the Principle. But the Principle of Good is universally known to all, and no one would do an evil act, never mind for its own sake. (For evil acts I mean the most serious crimes. Stealing, defraud or deceive someone, if they have no serious consequences, are not considered "evil" by Terrearthians, although they are still punishable by law)

Answer 1

Invent a new religion!

I'm not joking. The world you have described is very very very black and white: literally "everything is Good, except the shadow, which is Evil." This limits the amount of color you can put in your story.

Your shadow needs a weakness. In particular, here is a quad chart showing what happens when you mix good and evil

       Good     Evil
      +------+-------+
 Good | Good |  Evil |
      +------+-------+
 Evil | Evil |  Evil |
      +------+-------+

As you can see, by your description of "once the shadow infects an area, it becomes nothing" is an indomitable ability. That claim needs to be broken down in order to have Good ever stand a chance.

One bright solution is to bring in Chaos. Make the effect of mixing good and evil less predictable. If you mix black paint into white paint thoughtfully, it looks grey or black (depending on how much black you used). However, in the moments of mixing, you see swirls of black and swirls of white, unmixed. It is not unfathomable that after mixing Good and Evil, some swirls of Good remain, they're just hard to spot.

This forms the backdrop for what you really need: a new religion of balance. You intentionally have set up the Shadow to be ridiculously strong, so it will be hard for you to sell to your readers the idea that somehow humanity magically turns it back with a perfect plan. We're going to need something murkier.

Consider a new caste of individuals who are comfortable with a balance of Good and Evil, rather than merely worshiping Good. They can live off of the borders between them. These individuals would be able to see shades of grey, not just black and white. This ability would give them the ability to penetrate into the Evil Shadow for quite some time before losing their balance and being corrupted absolutely. If they could find the "core" of the Shadow, and instil one dollop of good in the center, it could weaken the shadow dramatically.

This would also generate political drama. The forces of Good could never appreciate what Those Who See Grey think, but they also would recognize that these individuals are the key to survival. The frustration of a perfectly good King having to trust a Grey individual would be palpable.

But the shadow would also seek out these Greys. They are not necessarily harder to corrupt or easier, just different. When corrupting good, the shadow must patiently wait in the dark, and strike when Good's defenses are down. With the Greys, it would be more of a continuous press, slowly trying to gain a foothold in their mind by making the Grey confused as to what is the Shadow, and what is the Grey itself (a confusion that is easier to have when Grey than Good).

---

As a possible source of this new Grey caste, consider the effects of an imperfect strike from Good onto Evil, or an imperfect corruption of Good by Evil. Both could create a mix which could create a sense of Grey. After all, The Shadow better make a mistake somewhere, or it really is too powerful of an opponent.

Answer 2

Starve the bastard!

If I understand correctly, The Shadow feeds by corrupting humans, and corrupted humans are only capable of evil. That excludes them from simple, mundane tasks, like harvesting food, sewing, cleaning up after themselves...

In other words, of the Good People manage to put some barrier between themselves and the land already claimed by the Shadow, and then use their magic to put themselves into 20 year slumber, two things will happen:

1. Human servants of The Shadow will die, since their only souce of food and medicine will disappear
2. The Shadow won't have anybody to corrupt, so it won't have a power source, and eventually run out of juice.

How to build such a wall is up to you.

I see from your comment to the other answer, that you want some boy form other world. Maybe you can make him some visionary engineer? We actually have a deficit of those in the real world, so maybe you'll inspire some young people to study math a bit harder :)

Answer 3

If it's a cosmic entity, defeat it in a cosmic way!

Say the entity has consumed half the planet. You can make the people of the people discover some kind of ancient magic that keeps their world together. Then, have them break that magic and split the world in two.

• This doesn't defeat the point of an eldritch abomination, which is to be so much beyond humanity that it can't be fought by conventional means.
• It doesn't eradicate the horror, since the Shadow can still make a comeback after a long while, if it finds a way to cross to the other half of the planet.
• Since the splitting magic will definitely be something arcane, you can have huge conflicts between the peoples of your world about whether they can and whether they should move forward with this.
• You will have an interesting setting to play with, in the stories between the initial "defeat" of the Shadow and its comeback- if you intend to write any.

Answer 4

If Druids can influence or control natural elements, I may have a solution: malachite. You see, malachite is known for trapping evil spirits. Your Shadow is the archetypal evil spirit, so if the Druids work together, they may be able to trap the Shadow in a giant malachite crystal. Then you'll have to be able to defeat it.

What if it's not someone dropping Good into the Shadow's core that beats it, but rather changing its paradigm? Paradigm=perspective, this Shadow clearly has a strong connection to people, so it's possible enough people with a strong perspective on "the beauty of nature" or the "meaning of life" could change its mindset and therefore its actions.

The genius of this is after the Shadow's eyes are (figuratively) open to how beautiful the world is compared to nothingness, it'll want to preserve the world as is, or maybe try to create a different version of the current world that better reflects its dark nature but isn't a "plain of absolute nothingness."