Might as well be a key
Some items are like a good utility knife: they have many uses. Other items are like keys: only useful when the game designer intends.
(This was originally written as a Sliding Scale article, but was renamed to be just about key items. This could use some rewriting to move all the Zelda examples out of the description.) Some items in video games have all sorts of uses. A standard sword in most fantasy/adventure games is useful for killing enemies, perhaps breaking pots or activating switches. There are things it can do that can also be accomplished by other means: it's possible to beat some enemies without it. Most importantly, the uses for it are widely varied and scattered throughout the game world in a way that doesn't seem at all contrived or awkward. Maybe it's even possible to use it for things that the game designer didn't necessarily anticipate, like herding animals. And then there are items that might as well be a key to a locked door: The game designer wants you to use them in a few specific places, there's no way to pass those places without it, and outside of those places the item is completely useless. A good example would be the Dominion Rod from Twilight Princess: It's only useful when there are statues specially meant to be controlled by it, and there's no way (barring glitches) to pass this obstacle without it. This isn't just about items that you are required to get to beat the game. The hookshot for example does have it's 'key' moments, where it's plainly obvious that you need to use it to advance, but those moments are a logical extension of the gameplay, rather than being a blatant 'must have this item to pass' obstacle. It's also not about Plot Coupons that magically open the way to the final dungeon when you've collected them all--This is about items you can actually use during player-controlled gameplay, and you can try using them whenever if you want--they just won't do anything, or will be practically useless. Weapons don't usually fall under this, but if you need an item to beat a specific enemy (especially a boss or mini-boss) and the item doesn't work on other kinds of enemies, it can effectively be more on the key side, especially if it turns the fight from impossible to extremely easy.
- All of the Zelda games have this in spades:
- Twilight Princess has the Dominion Rod, which has the ability to remote control statues, but those statues are only ever found in the Temple of Time, except for a Plot Coupon quest involving owl statues. There's also the Spinner, which fits into grooves designed specially for it, which are found in exactly one dungeon and two minor spots on the overworld map.
- Also in Twilight Princess, the coral earring, which you have to use to catch a certain type of fish in a certain spot at a certain time. You need it to get past that part, but there's really no other reason to have it, and you'll never have to use it again.
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