Ordinary weapons are pretty easy to use. Got a sword, slash with it. Got a gun? Point and shoot. But not this kind of weapon. This kind of weapon requires the user to offer up something in exchange for its use. (It could be Life Energy, an ally or anything of that sort.) This trope is popular in Video Games, as it allows the developers to create a way to limit usage of the more powerful weapons. (Especially Game Breakers.)
Note that this trope isn't exclusive to weapons- it can also apply to items, spells, abilities, or even Mons.
Compare and contrast sister trope Eye of Newt, which can overlap when the required ingredients are costly or painful to obtain, and can't be reused.
This trope can also overlap with the "cast from" tropes: Cast From Hitpoints, Cast from Lifespan, Cast From Sanity, and Cast from Money. (The last in particular covers more direct and literal uses of money, like using coins as ammunition, paying enemies to go away, or utilizing Practical Currency for its intended purpose.) If the payment is too exorbitant, it may result in the weapon/item/Mon being Awesome, but Impractical, and in extreme cases, the rarity of the required payment may mean It Only Works Once. Compare Powered by a Forsaken Child, and contrast Phlebotinum-Handling Requirements, where the magic carpet might not have a credit card slot, but only works if you're a left-handed mermaid.
- The Forlorn Hope in Yu Yu Hakusho demanded a life in return for its wish-granting powers. Subverted when Yusuke offered himself up instead of Kurama, impressing the spirit of the mirror and causing it to grant Kurama's wish by instead taking half the life of each, allowing both to avoid death.
- The Illusion Gate card used by Camula in Yu-Gi-Oh! GX required an offer of a soul in order to use. As the offering isn't specifically her soul, Camula would 'cheat' by using the souls of people her opponent cared about. The cost only has to be paid if you lose the game. Camula's Loophole Abuse creates a Morton's Fork for her opponent - since your soul is also on the line if you lose, you must either surrender the duel to save the sacrifice, sacrificing yourself in the process, or accept their loss and proceed to (try to) beat Camula. The latter is also easier said than done, as Illusion Gate is also a Game-Breaker. Said card also appears in the Yu-Gi-Oh! Tag Force Series, though its cost is replaced by losing 90 percent of the user's current Life Points at the end of the turn, possibly leaving them more vulnerable to the opponent.
- The three most powerful Caster Shells in the Outlaw Star universe are numbers 4, 9, and 13. Each of the sages on planet Tenrei can make one type, and they warn that they require so much mana to use that they'll convert some of your life force into mana to pull off their effects. In other words, don't use more than one at a time; you may not live through it.
- Horizon in the Middle of Nowhere has an extremely literal example. Shiro's contract with the God of Commerce allows him to form a contract to borrow the powers granted by other deities. Provided he pays for it and the bill goes up the longer he uses the powers and the more he borrows. In a more general sense, this is one of the strengths of shinto spells. Rather than relying solely on the caster's power you can make a contract with a patron deity and then make "offerings" to increase the power of spells or to trigger some special effects. The nature of the offering and the spells and abilities they offer depends on which god a contract is made with.
- In Castle Town Dandelion, Kanade's Power of Creation requires her to pay for the things she materializes, or else something else she materialized will dematerialize to pay for it.
- The Yu-Gi-Oh! TCG has many cards that have some sort of cost, being it offering a monster as a tribute, discarding cards from the hand, removing cards from play, or paying Life Points.
- Magic: The Gathering has cards that have activated abilities that usually require an additional cost to use, otherwise they sit on the battlefield idly. These costs are often in the form of additional mana payments, though they may also include sacrificing permanents, paying life, discarding cards, or other miscellaneous actions. Some creatures can't even attack or block unless you fulfill an additional cost, offsetting their incredible power-to-cost ratio.
- The Mummy Returns, the second film in The Mummy Trilogy series with Brendan Fraser. The Bracelet of Anubis has to be inserted into the mouth of the scorpion statue to bring forth The Scorpion King. What isn't mentioned is that it then melts the hand/arm used to insert it. Too bad for the Curator, eh?
- Nightblood from Warbreaker consumes its wielder's Breath when drawn to fuel its ability to vaporize anything you hit with it.
- Friday the 13th: The Series: Some of the Devil's artifacts required that the user pay a price for their use, such as a lantern that found sunken treasure but required the death of one of the finders afterward. There was also a crucifix with a hidden blade that required the user to kill a living person before the crucifix could be used to destroy vampires.
- Kamen Rider:
- In Kamen Rider OOO, the Cell Medal coins the monsters are made of are used to power various weapons, such as the Ride Vendor and the Candroid support robo-critters it dispenses when it's not being a Cool Bike. The machine has an actual coin slot that medals are inserted into before it will transform or dispense a Candroid. The Medajalibur sword is only a partial example, since it can be used normally but requires medals to perform a Finishing Move. OOO's suit is itself powered by Core Medals, but unlike Cell Medals they aren't expended when he transforms.
- Kamen Rider Birth is an even better example. In addition to having access to the Ride Vendor and Candroids the same as OOO, everything needs a Cell Medal to activate. Need to transform? Insert Cell Medal. Need to activate one of the secondary weapons? Insert one Cell Medal for each. Need more ammo for your gun? Use the attached canister to load in a heap of Cell Medals. Need to fire the Breast Canon (a chest mounted weapon)? Insert one Cell Medal to summon it and at least one more to fire it (more Cell Medals means a more powerful shot). Need to summon Sasori CLAWS (a robotic scorpion formed from combining the secondary weapons)? Insert 1000 Cell Medals (at least for the first use).
- Dungeons & Dragons:
- Many powerful spells require some form of expensive Eye of Newt as a way to mitigate their game-breaking potential.
- Module I12 Egg of the Phoenix. The sword Chrysomer demanded that its wielder encrust 5,000 gold pieces worth of gemstones on it each month or it would refuse to use its powers.
- Module WG4 The Lost Caverns of Tsojcanth. In order to power the artifact Daoud's Wondrous Lanthorn, the user had to put thousands of gold pieces worth of crushed gemstones in a built-in compartment.
- Module WG7 Castle Greyhawk. In order to use a magical set of stairs (Ascendus' Scandent Coin-Op Acclivity), the user had to pay an increasing number of silver pieces to ascend each step.
- The Ravenloft setting has a giant magical bowl that could allow escape from the plane but requires human sacrifice to use.
- Changeling: The Lost has Tokens, items that have been suffused with the magic of the Hedge. Changelings can activate them by expending Glamour or exerting their measure of the Wyrd, but anyone can activate them if they pay the Catch. Depending on the Token, this could be a pint of blood, your luck at romancing others for the rest of the week, or a handful of dead fireflies.
- Yojimbo from Final Fantasy X sometimes demands gil first in order to work for you, then again every time you needed to attack, depending on how much he likes you. If you know his mechanics, you can raise your chances of him using his ultimate One-Hit Kill technique (which can potentially one-shot even Penance) without paying him a single gil to something fairly reasonable. There's a guide on GameFAQs devoted entirely to his mechanics.
- The Yoto Swords in Tenchu: Wrath of Heaven require a payment of life to use. There are two ways to meet the requirement: Using the swords to kill living enemies satisfies the payment, but if you don't do that, simply having the swords equipped will slowly drain your life. The upside is that these swords can be used to kill undead enemies, which ordinary swords can't do.
- The bow in The Legend of Zelda used your money to represent the supply of arrows (presumably, Link used the rupees as arrowheads), while the Magic Armor in The Legend of Zelda: Twilight Princess drains your money to protect you from damage. These are likely attempts at averting the usual Money for Nothing scenario.
- Money in Mystical Ninja Starring Goemon, at least for Nintendo 64, is a weapon.
- In a continuation of the original Ghostbusters movie, an episode of The Real Ghostbusters showed what happened when they didn't dispose of their contaminated uniforms; they wound up with evil counterparts made of ectoplasmic energy. However, as Egon noted with their attacks, "Each time they fire, they weaken." Meaning, according to Ray, "The more they use, the less they have."