Atium
Atium is one of the two god metals. An Allomancer burning atium is able to see into the future by a few seconds. Feruchemists can use atium to store age, and when used as a Hemalurgic spike, atium steals any property or power.
Atium is notable as it is the condensed power of the Shard Ruin. It was sequestered away at the Pits of Hathsin by Preservation when the latter gave up his mind to trap Ruin.
Allomantic Use
An atium Misting is known as a Seer. Burning atium allows the user to see a few seconds into the future, and expands the user's mind to be able to accept and process all of the information. If another Allomancer burning atium is encountered, the atium ghost will split, since each seeing into the other's future means that they can both make different decisions that affect both Allomancer's outcomes.
Burning duralumin with atium will allow an Allomancer to see the ultimate effects of his actions.
Alloys of atium produce various expanded mental and temporal effects.
Feruchemical use
Atium, when used by a Feruchemist, stores age. When storing age, the Feruchemist spends time older. It is possible to then burn an atiummind to get an enormous burst of youth - allowing for practical immortality.
Hemalurgic Use
When used as a Hemalurgic spike, atium is like a wild card. Depending on where it is placed, it can steal any Hemalurgic property.