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A common staple of fantasy is that someone or something needs to be overthrown and/or defeated. To do this, there's often a protagonist and their entourage, or, more often nowadays, an antihero who struggles with the concept of helping anyone, going on a journey to fulfill their goal. Along the way, powerful weapons are commonly used. Or, in the case of a weapon like the One Ring from The Lord of the Rings, a weapon needs to be destroyed.
Although weapons in fantasy books come in all shapes and sizes and don't have to be traditional weapons like swords or knives, with the Elder Wand from Harry Potter being a famous alternate example, the most powerful (and often, overpowered) weapons do tend to be blades in one shape or another. These dangerous blades can be, in fact, very creative, with great abilities, magical prowess, and occasional dark intent.
The Elric Saga's Parasitic Stormbringer Brings New Meaning to a Toxic Relationship
Stormbringer from The Elric Saga is one of the most chaotic blades in fantasy. It is a sentient, intelligent, and powerful blade, capable of giving its owner strength and vitality. Even a weak man like Elric of Melniboné could become one of the strongest in the land just by owning Stormbringer. However, with great power comes a lot of downsides.
The sword is, in fact, a demonic entity that is almost like a vampiric parasite. Anything struck by the sword has its life force drained and absorbed by the blade, thus satiating it for a time. This life force is then directed into the sword's master, giving them incredible strength. The malicious sword can cut through virtually anything, but it desires flesh most. This leads to the sword occasionally taking command of the user and leaping forward into combat, which can have disastrous results, where users like Elric can kill those they love.
His Dark Materials' The Subtle Knife Demands Much From Its Bearer, but Can Open Doors to Different Universes
For a tool that can alter reality, The Subtle Knife from His Dark Materials is actually a rather straightforward weapon in terms of abilities (and is the only weapon that isn't a sword on this list, although it is still a blade). One side of the knife functions like a powerful blade would and cuts through materials, but it can cut through any living or nonliving matter in any universe. The other edge of the blade is the more worrisome one, as it can cut through the fabric of the universe itself, opening portals to other worlds.
Although this is an incredibly powerful tool in the universe of His Dark Materials, there are some catches. One, the one who owns and uses the blade, will lose two fingers in the process. There are no exceptions, as this is the mark of the bearer. Another is that if one doesn't cut the space between dimensions correctly, it can lead to permanent damage where dark Spectres (beings that eat souls) are formed, and Dust can leak into other worlds. Lastly, the blade is prone to breaking, and a bearer who has too much love in their heart can shatter it.
Wheel of Time's Callandor Has Unlimited Potential
On the outside, Callandor from The Wheel of Time looks like a unique longsword, but it is actually a sa'angreal. These are tools that can magnify a channeler's connection to the One Power, which is a magic system that certain people can access. However, Callandor is different from the other sa'angreals in that it is a legendary sword tied to a prophecy and is only able to be drawn by the Dragon Reborn (in The Wheel of Time, this is Rand), and it can also be connected to True Power (the power the Dark One connects to).
It is the only sa'angreal sword, and is especially unique since its crystal blade can cut and redirect balefire. But the main difference it carries is that, unlike other sa'angreal, Callandor has limitless potential. However, this is also a downside for those who are unprepared to wield such power, as channelers can get burnt out and/or become overwhelmed and go mad. When men use it by themselves, they can also be controlled by female channelers against their will due to their steadier nature with the One Power.
Stormlight Archive's Nightblood Is the Personification of the Word Obliterate
Although established in the Warbreaker book, Nightblood has been seen in multiple wildly popular Brandon Sanderson books, most notably The Stormlight Archive. Due to this, it's seen as the strongest weapon in the extended Cosmere universe. Forged with the intent to destroy evil, the sword mimics a Shardblade, which can sever souls from a body and can pass through most matter, but it has a few key differences that make it as powerful as it is.
First, Nightblood doesn't just sever a soul; it destroys it and the body entirely. Additionally, it's sentient, but cannot make sense of morality and relies upon its wielder to decide such terms. This, however, becomes a problem with the other big difference regarding Nightblood - how it gains power. Whereas other Shardblades need no help to fulfill what the owner desires, Nightblood requires large amounts of Investiture (magical energy) and can coax owners into madness when deprived of it.
In terms of immediate results, there's a strong case for Nightblood to be the most powerful weapon in all of fantasy. However, the sword has a few limitations and issues that make it slightly less devastating in the long term. Some, like driving owners to madness and death, are mentioned above. But in addition, although Nightblood can destroy almost anything, it cannot destroy aluminum. It is also an oddly emotional blade, easily tricked and prone to anger and hunger.
Malazan's Dragnipur Is a Soul-Sucking Blade That Carries a Heavy Weight
There are many swords within fantasy that are more than just metal blades, some with magical properties or special functions. But the Dragnipur from the Malazan Book of the Fallen series is more than just a sword; it's a black blade that carries the power of the cosmos. The massive sword itself has a pocket dimension embedded within it, and every soul killed by the sword is trapped within this dimension, no matter if the soul is human, creature, or divine.
With each soul collected, the blade becomes heavier, and the sword requires countless new souls. Although there is no definitive number of souls inside the dimension, the blade is said to carry a countless number, enough for legions upon legions, and Rake is only able to carry the sword due to his immense strength as an Ascendant. Within the sword, the souls are then forced to carry out the will of the Elder God Draconus (the one who forged the blade).
So, what is his will? Well, only that each soul must forever pull the Gate of Darkness away from the real force of Chaos, in a cart no less. This pocket dimension is soon seen as a world of its own where battles take place, and is where Anomander Rake himself goes after sacrificing himself to the Dragnipur. Within the sword and alongside the god Hood, Rake is able to destroy the cart and obliterate the sword from within, allowing the Gate of Darkness to escape its binds and be free from the threat of Chaos, thus saving the world.
