Metallic Arts (Cosmere)

The Metallic Arts refers to three related magic systems that appear in the fantasy book series Mistborn and its sequel series Wax and Wayne by Brandon Sanderson. These are named Allomancy, Feruchemy, and Hemalurgy. They all make use of the same sixteen metals listed below.

Allomancy
Allomancy is the inherent ability to "burn" metals in the Allomancer's body to give rise to a supernatural effect determined by the metal in question. Allomancy is end-positive; when a user consumes and burns metals, a Connection is formed with the cosmic force of Preservation and energy is gained. There are sixteen Allomantically invested metals; eight pure metals (from the periodic table) and a specific alloy of each of them. Trying to burn a non-Allomantic metal, or an Allomantic alloy with the wrong proportions of included metal causes malaise, or possibly even death. Allomancers can be divided further into Mistings and Mistborn. A Misting is born with the ability to burn only one of the sixteen Allomantic metals. A Mistborn is born able to burn all sixteen. (For context, it should be noted that later in the Mistborn world [Era 2] full Mistborn are no longer born.)

Feruchemy
Feruchemy is the inherent ability to store quantities of specific attributes in pieces of metal (dubbed metalminds in-world), to be retrieved at a later time. The specific attribute that can be stored in the metal is determined by the metal in question. Feruchemy is end-neutral; when the user retrieves the attribute from the metal, they cannot gain anything more than what is still stored in the metal, though the Feruchemist can control how much they retrieve and how quickly. An important ground rule is that what has been stored in a specific metalmind can only be accessed by the Feruchemist that stored it in the first place, not by others. There are sixteen Feruchemically invested metals, the same ones as used in Allomancy. Other natural metals have no uses in Feruchemy. Feruchemists can be divided further into Ferrings and true Feruchemists. A Ferring is born with the ability to make use of one of the sixteen Allomantic metals. A true Feruchemist is born able to burn all sixteen metals. (For context, it should be noted that Ferrings appeared in later times in the Mistborn world when true Feruchemist were no longer born.)

Hemalurgy
Hemalurgy is not an ability to be possessed, like Allomancy or Feruchemy, but instead a form of magical procedure through which attributes or abilities may be granted to those born without them, or through which existing attributes or abilities in someone might be enhanced. This is done by killing the original owner of such an attribute or ability with spikes made of one of the metals used in the Metallic Arts and inserting those spikes into certain positions in the new host's body. The abilities or attributes remain as long as the spikes remain. Hemalurgy is end-negative; when creating the spikes and stealing the victim's ability or attribute, some of it is lost in the process and the receiver of the Hemalurgic spikes gain an amount of ability or attribute that is lesser than what the original owner possessed in life.

Compounding
It is possible to have both Allomantic and Feruchemical powers. A person can be born as both a Misting and a Ferring; such a person is known as a Twinborn (for context, this situation never happened in the first book series and became relevant first in the second book series). The two abilities a Twinborn have don't have to be tied to the same metal; by virtue of probability, since the metals are chosen at random, it is highly improbable a Twinborn will have Allomantic and Feruchemical ties to the same metal. However, when a Twinborn is born with both Allomantic and Feruchemial ties with the same metal, they are able to use a phenomenon known as Compounding.

In Compounding, an attribute is first stored in a metalmind through Feruchemical ability. Then, the metalmind is tapped to withdraw that ability, but while the attribute flows out, the Compounder is able to fuel the Feruchemical trait through Allomantic means, increasing its quantity. This means that a Compounder can effectively have an unlimited amount of a trait that they would normally have to store up over long periods of time. This behavior was an unforeseen consequence of the intermingling of the Allomancers and Feruchemists, bending the end-neutral nature of Feruchemy.