Mistborn

A Mistborn, or Allomancer, is a person who has discovered the ability to manipulate their surroundings by ingesting metal and destroying it in their stomach. For those unprepared, they are insurmountable foes.

Metal Magic

When you ingest a metal, you have the option to "burn" it, destroying it in exchange for unlocking its hidden power. Burning a metal can be done without an action, but doing something with it does. Once you perform an action with the burning metal, you will be burning it until the start of your next turn, in which you can choose to stop. You lose 2 grams of metal when doing this. Different metals do different things, and one not listed may severely harm the Allomancer when burned:

     Iron: When someone burns iron, they gain the ability to pull any type of non-aluminum metal object towards them. An iron-burner can also see otherwise invisible blue lines between their chest and any metal objects in range, allowing them to detect metal as well as move it. If a force equivalent to their own weight couldn't move an affected object, the Allomancer will be pulled toward it instead.

     Steel: When someone burns steel, they gain the ability to push any type of non-aluminum metal object away from them. Steel functions exactly the same as iron, but instead of decreasing the distance between Allomancer and metal, it increases. This is commonly used to push projectiles, for example coins, at opponents at high speed or to fly through the air by pushing on metal below.

     Tin: Someone burning tin gains enhanced senses, taking in more of their surroundings. They can see and hear from farther away, take in smell much better (although not to the extent of something like a dog), and gain more acute awareness of what they're touching. Tasting also applies too, but that's not too helpful most of the time. An Allomancer currently burning tin gains +2 on all Perception, Investigation, and Insight checks, as well as any other checks that have to do with their physical senses.

     Pewter: Someone burning pewter gains physical prowess, growing stronger, tougher, and more dexterous. A pewter-burner's Strength, Dexterity, and Constitution modifiers are doubled while they are burning the metal.

     Copper: Allomancers burn copper to hide their allomantic energy from anybody looking, as well as those around them in a 5 foot radius, increased by an additional 5 feet for every level above 1 in Rogue. Bronze burners cannot find you while you burn copper, and anybody using an Arcana check on you has disadvantage.

     Bronze: Allomancers burn bronze to sense the location of anybody nearby who is using allomancy (a.k.a. burning a metal). They can also sense what type of metal they are burning if they are familiar with it. Copper nullifies this ability unless the one burning bronze is very powerful or using duralumin, and using duralumin in response negates it.

     Zinc: When someone burns zinc, they gain the ability to enflame the emotions of those around them, causing them to feel more strongly about something. If one pushes too hard, it could notify the affected person that something is not right, but a careful Allomancer can avoid that. When you are burning zinc, you get +2 to Persuasion, Intimidation, Insight, and Animal Handling checks when you are trying to encourage the animal to do something.

     Brass: When someone burns brass, they gain the ability to soothe the emotions of those around them, causing them to feel less of some emotion. If one soothes too much, it could notify the affected person that something is not right, but a careful Allomancer can avoid that. When you are burning brass, you get +2 to Persuasion, Deception, Insight, and Animal Handling checks when you are trying to calm an animal down.

     Gold: Allows an Allomancer to see an illusory version of themself showing what they might be like if they had made different choices in the past, or maybe just a past version of themself. No one really knows.

     Electrum: Allows an Allomancer to see illusory versions of themself performing the potential actions they could take in the next few seconds.

     Cadmium: An Allomancer burning cadmium can create a stationary bubble centered on them in which time moves much slower, the radius being 5 feet, with an additional 5 feet for every 2 levels in Rogue above 1. Sentient beings can't enter or exit the bubble, and projectiles entering may have an unpredictable trajectory. The speed of time inside the bubble can be from 1/2 as fast to essentially the Time Stop spell (looking at it from the outside). The metal burns at the rate of time it is inside.

     Bendalloy: An Allomancer burning bendalloy can create a stationary bubble centered on them in which time moves much faster than outside. It is essentially the reverse of cadmium, and the same rules apply, including those for size and time dilation.

     Aluminum: When burned, aluminum instantly burns all of an Allomancer's metals without any of their effects.

     Duralumin: When burned, duralumin uses up extremely quickly any metals that the user is also currently burning. Burning it causes you to take all numbers in the description of the metal you're burning and multiply them by the amount of grams you have left times 2, plus one, in exchange for the entirety of that type of ingested metal to be gone at the end of the current turn. Duralumin can be burned as a reaction instead of an action.

     Chromium: If you burn chromium and touch another Allomancer, it has the same effect that aluminum would have on them. Their metals will be completely drained with no effects.

     Nicrosil: If you burn nicrosil and touch another Allomancer, it has the same effect that duralumin would have on them. Their current burning metals will be burned all at once, greatly enhancing their effects.

Unintended Repercussions

When you attempt to burn a metal that is too impure or one without abilities attached, it wreaks havoc on your body. Take 3d8 poison damage at the start of every turn you are burning the bad metal, and you cannot burn any other metal while doing so. Give your Strength modifier a multiplier of 0 for 2 days per turn you burn the metal. This same weakness effect applies for a day if you leave any metal in your body when you take a long rest, because that's unhealthy.

Flare Metal

When you burn a metal, you have the option to "flare" it, burning more at once to increase your power. When you flare a metal, treat any number in its description like it's multiplied by 2. Flaring can be started at any time (even another player's turn), but starting to flare a metal uses 1 gram of it, and will consume another gram at the beginning of any turn. You cannot stop flaring until the beginning of the subsequent player's turn, so doing it will cost 2 grams at least. Flaring cannot be done while burning duralumin.

Alignment Metals

You, being a level 13 allomancer, can now burn 4 extra metals:

Mithral: This light, durable metal, oft used for more streamlined purposes, will allow allomancers to quiet the power of shadow or death up to (20 ft. x their rogue level above 8) away from them. When burning, you can at any time reduce necrotic damage from any source by (your rogue level -11)d6; however, you can only do this (your rogue level -8) time(s) between one of your turns spent burning and another.

Valythnium: A rarely-produced alloy of mithral, this metal allows the burner to stir the souls of the dead, amplifying necrotic damage from chosen attacks. The same range and number of targets applies as mithral, and you increase necrotic damage at the same rate mithral diminishes it. 

Adamant: The purer form of the oft-mentioned adamantine, it gives the burner the capability of amplify the brightness of light in the nearby area (20 ft. x their rogue level above 8). When used to the normal output of 2 grams per turn cycle, anybody in the path of (your rogue level-8) chosen sources of light takes (your rogue level -11)d6 radiant damage at the beginning of their turn spent there. They also must make a DC 8 CON save to avoid being blinded for 2 turn cycles unless they close their eyes, effectively blinding them anyway. You can also add that same amount of radiant damage to attacks within range that use it, but only (your rogue level -8) time(s) per turn cycle.

Adamantine: This alloy of legends, when not used for armor or weaponry, can give allomancers the ability to dim any light, magical or otherwise, in their surrounding area. The same range and number of targets applies as adamant, and you reduce radiant damage coming at you by the same amount that adamant dishes it out.

Experienced Mistborn

 As a level 17 Rogue, you get one reaction during the other players' turns to burn or stop burning one metal, with a second one that can be used only for duralumin.