A dial is a swirled shell from an extinct magical creature that used to live high up in the skies on land made of ancient, fossilized clouds. The sky people use them to power much of their technology, and, on occasion, will trade them to explorers from the ground level who manage to make it up there.
Dials have the ability to absorb and store energy, or sometimes matter, and then release it when a discreet button on the shell is pressed. Each dial can only absorb and release something specific, so different dials have wildly different uses.
Impact Dial - These dials absorb blunt impacts. The momentum of a blunt attack is completely negated if it hits an impact dial. A palm-sized dial can absorb 6 points of damage, and once fully charged, will deal d6 damage if used in combat. These can easily be charged up simply by hitting them with a hammer, or even your hand if done enough times. If positioned and braced carefully outside of a combat, their destructive power is even greater, as if multiple hammer blows all landed simultaneously on a single point.
To charge: an impact dial in combat, first let your enemy automatically hit you. Then, make a saving throw. If successful, you have negated the attack. Otherwise, you're hit automatically.
Axe Dial - Same as Impact, but it absorbs slashing attacks. These are much rarer, and function as "+1" Impact dials. Their energy is released over such a small area that it could easily cut through an iron bar.
Heat Dial - Stores thermal energy, and emits a flame. A handheld heat dial on its own probably won't be useful in combat, but it's basically a portable stove-top / blowtorch.
To charge: Put in a fire, or similarly high heat environment for an hour.
Flavor Dial - These dials absorb whatever smell or flavor they are immersed in. They can be used to flavor something, or if you're more devious, they can emit capsaicin or farts in the faces of your enemies.
To charge: Put in a flavorful environment. Hang above your pot when cooking, or keep it in a bag full of spicy peppers for a day.
Breath Dial - These store whatever gas they are immersed in. Like Flavor dials, but they actually store and emit a large volume of gas. Whether that's air, poisonous gas, or hydrogen. They can be tuned to emit the gas to generate force, but not as great as a Jet Dial.
To charge: Simply keep it surrounded by the gas that you want it to absorb. Above a campfire to fill it with smoke, or in a gas filled cave.
Jet Dial - An advanced, rarer form of the Breath Dial. These emit their stored gas all at once, causing a rocket-like force.
To charge: They need to be charged up with both force and gas. So, they would charge easily in a high pressure atmosphere, or they need to be pointed towards the wind and blown into, whether you strap it to a windmill or blow into it like a balloon.
Flash Dial - A dial that absorbs light. When activated, emits a blinding flash of light all at once. Lamp Dials are related, but release their light slowly over time.
To charge: Sit it in sunlight for an hour, or in firelight for a day.
Tone Dial - Basically a handheld recorder. Make a sound into the shell, then press the button to replay it.
To charge: Just speak into it!
All of these dials can come in widely different sizes. Your average adventurer might mostly want handheld dials, but larger ones have both more capacity and can generate a much higher force when used. You wouldn't take a car engine sized breath dial dungeon delving, but you could use it to build a jet-ski.
In general, I think inventor type characters should be able to tweak the intensity of a dials emitted force. For example, a character that modifies his Heat Dial to emit all it's stored force at once as a big fireball. Or, as mentioned above, modify a breath dial to propel itself forward.
I generally like that a dial does something super specific, but that the effect has a super wide range of uses. They're another tool to have on your belt to solve open ended problems.
What type of Dial did I just find? d20
1-3 Impact
4-6 Heat
7-10 Flavor
10-13 Breath
14-16 Flash
17-18 Tone
19 Axe
20 Jet
How big is this dial? d12
1-9 Handheld
10-11 Loaf of bread sized
12 Car engine sized
There are more dial types, and examples from the comic here: https://onepiece.fandom.com/wiki/Dials
PS: Not gonna lie, I really want to play in a game where I can be fighter who has a shield completely COVERED in impact dials
