Only with this can you take down the Big Bad.
Whoa, not so fast there, sport! You can't go rushing out on your way to punch out Cthulhu. You see, the Big Bad is way too powerful for you to handle at your base power. You would be dealt a Curb-Stomp Battle in probably less than a second. However, there is a way to defeat him. It doesn't just make the Big Bad easier to deal with, it's the only way to take him down. There is an artifact that has the ability to take him down, but it's able to be handled by anyone. It may be because the villain is an embodiment of evil and said artifact is made of enough goodness that it smites his evilness. It may be because the object is an Amplifier Artifact that boosts the hero's power to match the villain's. In that case, it's best to be careful with it so that it does not fall into the villain's hands. Subtrope of Plot Coupon That Does Something. Sister Trope to Sword of Plot Advancement.
- His Dark Materials has what is a subversion of this. The subtle knife is claimed more than once to be the only weapon capable of killing God (the supposed Big Bad of the series), and its owner is urged to take it to the guy opposing God so he can win the war. Then God turns out to be too old and senile to be the Big Bad, and simply dies of old age.
- Gardner F. Fox's "Niall of the Far Travels" short story "Out of the Eons". Ages ago Adonair, an evil deity from another universe, tried to conquer the world and enslave humanity. The native gods could not destroy him but managed to trap him. At the beginning of the story Niall accidentally frees him. The only way to destroy Adonair is for Niall to drink a special white liquid (that was created by the gods at the same time as they originally trapped Adonair) and trick Adonair into possessing his body.
- A special Colt gun and bullets, made by Samuel Colt himself, can be used to kill practically anything - but not Lucifer.
- There's a special dagger which is used to kill demons (and the human they possess at the time). Regular daggers don't kill demons, just the host body. Its backstory has yet to appear.
- In one episode the Monster of the Week is a dragon. As Sam & Dean learn, the only way to kill a dragon is with a sword forged with the blood of a dragon. Dean points out the anomoly: "So you need one [sword] to kill one [dragon], but you got to kill one [dragon] to make one [sword]. How does that work out?"
- Buffy the Vampire Slayer had some of these-such as Thor's Hammer, used to whomp Glory down to size.
- Subverted in the Doctor Who episode "Last of the Time Lords." The episode features Martha Jones spending a year trying to locate a weapon divided into four parts that can defeat the Master, only to reveal at the very end that the Villain-Beating Artifact was a ruse to distract from Martha's real goal.
- Once Upon a Time has a twist on this trope. The only way to bring down the Big Bad is to steal his dagger, but then you become the villain yourself.
- In most games in the Zelda series Link needs the Master Sword to defeat Ganon. Likewise, the Phantom Sword in Phantom Hourglass is needed to defeat Bellum.
- Also from Zelda, the Silver Arrows (at least in A Link to the Past).
- The Three Sacred Treasures in Kid Icarus and Kid Icarus: Uprising are needed to defeat Medusa. Pit later tries to use them to kill Hades in Uprising, but Hades blasts them into nothingness. Pit then went to Dyntos to receive the Great Sacred Treasure, which fared much better, but it also got destroyed, but Pit and Palutena manage to kill Hades by using the Great Sacred Treasure's Wave Motion Gun on him, powered with Palutena's power.
- Sonic the Hedgehog games have traditionally ended with Sonic (and sometimes whatever ally he has at the time) using the Chaos Emeralds to go super, since the Final Boss would be too powerful otherwise, and much of the time, they're out in space or otherwise flying, which Sonic can't do on his own. Though, he does later prove he can take down Chaos, the former Final Boss of Sonic Adventure, in Sonic Generations without the Chaos Emeralds, or at least he has grown much in strength since then.
- In Neverwinter Nights 2, The Silver Sword of Gith is the only weapon capable of harming the King of Shadows. Unfortunately, it was broken into several shards the last time it was used, and your character isn't the only person interested in collecting them.
- One quest in Arcanum requires you to find a specific dagger so that you can kill a wizard whose soul is bound to a demon. Killing the wizard with any other weapon will release the demon into the world. Also, the final boss can only be killed with one of two items, the Vendigroth Device or Kryggird's Falchion.
- In the God of War series, the power contained within Pandora's Box is the only thing capable of killing a god. Kratos spends the first game trying to find and open the box so that he can defeat Ares. In God of War III he needs to open it again in order to defeat Zeus...or so he's led to believe, as the box is, in fact, still empty since the last time he opened it.
- The original version of Doom 3 requires that the player use the Soul Cube (which they get early on) to take care of the final boss Cyberdemon. The other, smaller demons, however, weren't limited to such a weakness, not to mention the fact that the Soul Cube uses the souls of fallen enemies to power it up enough to take on the Cyberdemon. This is subverted both in later patches of single-player mode and in co-op mode.
- Warcraft 3: not a specific weapon, but a damage type. Divine armor is only affected by Chaos damage, which is mostly reserved for the Legions of Hell or extremely strong monsters. In order to defeat the otherwise invulnerable demigod Cenarius, Grom Hellscream's orcs reactivate a demonic pact, allowing them to defeat him(by giving them Chaos damage).
- Also, Illidan devours the Skull of Guldan which the Legion was using to spread corruption throughout the Night Elves' forests. This transforms him into a half-demon, and gives him the ability to defeat the demon Tichondrius.
- In Chrono Cross, you can kill the Time Devourer just using force, but using that method, it's able to come back. The only way to kill it permanently is using the Chrono Cross.
- Distilled down to its essence in Grow RPG: in addition to the best sword and armor, you've got to have the special blue orb that knocks the Big Bad's health meter down to where you can actually trade hits with it. (It may not be possible to reach the Big Bad without it, though.)
- In Samurai Jack, the title character's sword is the only weapon capable of taking out Aku, since the sword was forged out of goodness.
- The Elements of Harmony in My Little Pony: Friendship Is Magic, wielded by the "mane six", were needed to take down two villains: Nightmare Moon and Discord. Celestia suggested that they use it on the Changeling Queen, but they never get the chance to use it due to being captured before that can happen.
- The Dreamstone is depicted this way, being the key to giving the heroes good dreams and protecting them from Zordrak's Argorribles giving them nightmares. Oddly however in a couple of instances the Dreamstone was stolen, the argorribles could be neutralized and scared away rather handily by alternate magic, leaving wonder as to why the heroes and villains see it as so pivotal in the first place.
- In Adventure Time, Billy's gauntlet has the power to seal the Lich. The Lich destroys it before Finn can use it against him, and Finn ends up using the Power Of Liking Someone A Lot to destroy his physical form.
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