Atium is a god metal. An Allomancer burning atium is able to see into the future by a few seconds. Feruchemists can use atium to store youthfulness, and when used as a Hemalurgic spike, atium steals any property or power. The metal is a reflective, silvery color, so much so that beads of atium almost appear to be drops of liquid.
Presumably, the name "atium" is inherited from Ati, the name of the original holder of the Shard Ruin, just as the name "lerasium" is inherited from Leras, the original holder of the Shard Preservation.
An atium Misting is known as a Seer. Burning atium allows the user to see a few seconds into the future, by producing atium shadows of everything in sight. These shadows perform future actions. Burning atium expands the user's mind to be able to accept and process all of the information, even allowing the Allomancer to dodge incoming attacks from behind. If another Allomancer burning atium is encountered, the atium shadows will split, since each seeing into the other's future means that they can both make different decisions that affect both Allomancers' outcomes. An Allomancer's atium shadow will also split when burning electrum.
Burning duralumin with atium will allow Allomancers to see the ultimate effects of their actions, allowing them to peer into the Spiritual Realm. Aluminum objects do not generate atium shadows.
Atium, when used by a Feruchemist, stores youthfulness. When storing youthfulness, the Feruchemist spends time older. When tapping youthfulness, the Feruchemist then spends time younger.
When used as a Hemalurgic spike, atium is like a wild card. Depending on where it is placed, it can steal any Hemalurgic property and it does so better than other spikes.
Atium may also be alloyed with any of the other Allomatic metals. However the only currently known atium alloy is malatium, an atium-gold alloy. These alloys grant various expanded mental and temporal effects when burned.
As atium is a god metal, it does not form naturally. The metal only came to exist when Preservation stole a chunk of Ruin's power and created the Pits of Hathsin, where atium grows in crystals, to deny Ruin's access of part of his power. During the Final Empire, atium is classified as one of the two high metals along with gold and was thought to be only accessible to Mistborns. However, atium mistings did exist. Due to the scarcity of atium and the Lord Ruler's intended misleading, such existence was unknown to most people until the exception of Yomen occurred. The Steel Ministry sometimes blend atium into food during a ball, to find out hidden atium mistings. These people can be used to make Steel Inquisitors or put to other usages. 
Actually, the atium mistings are not natural. Supposedly, there are only sixteen kinds of Mistings, one for each kind of basic metal. But Preservation altered this as a part of his plan to defeat Ruin. The atium Mistings serve as a way to burn away Ruin's power without being affected so much by the destructive Intent. Also, when the mists started to snap people, one sixteenth of them became Mistfallen, whom were later found out to be atium mistings.
After the catacendre, Sazed changed the Allomantic table back to normal and atium Mistings no longer exist.
During the time of the Final Empire, atium could only be mined at the Pits of Hathsin, run by the nobles of House Venture. Several days before the fall of the Final Empire, because of Kelsier's second visit to the Pits, the atium mine is destroyed.
After the Catacendre, it is possible that atium still grows somewhere, but nothing is known about it.
- Atium is different from other Allomantic metals in that when it (and presumably its alloys) is burned, it provides the power from Ruin rather than Preservation, since it is of Ruin.
- Harmony speculates that atium makes the Allomancer burning it a more efficient killer since it draws upon Ruin's power.
- Alloying atium and lerasium after Ruin and Preservation combined will not give harmonium. Splitting harmonium through distillation will give something different from atium and lerasium. While difficult, it is possible to split harmonium through distillation to get atium and lerasium.
- The Final Empire chapter 13 #
- Mistborn Adventure Game chapter 15 #
- /r/books AMA 2015
— Arcanum - 2015-08-01#
- Words of Radiance San Francisco signing
— Arcanum - 2014-03-06#
- The Final Empire epilogue #
- Hero of Ages Q&A - Time Waster's Guide
— Arcanum - 2008-10-15#
- Barnes and Noble Book Club Q&A
— Arcanum - 2009-07-08#
- Tor.com Q&A with Brandon Sanderson
— Arcanum - 2011-01-10#
- Annotation for The Hero of Ages chapter 71 #
- The Hero of Ages chapter 78 #
- Skyward Houston signing
— Arcanum - 2018-11-19#
|The Metallic Arts|
|Arts||Allomancy · Feruchemy · Hemalurgy|
|Concepts||Metalborn · Snapping · Savants · Metalminds · Twinborn · Compounding · Blessings|
|Constructs||Steel Inquisitors · Koloss · Kandra · Chimeras|
|Base Metals||Iron · Steel · Tin · Pewter · Zinc · Brass · Copper · Bronze · Cadmium · Bendalloy · Gold · Electrum · Chromium · Nicrosil · Aluminum · Duralumin|
|God Metals||Atium (Malatium) · Lerasium · Ettmetal · Trellium|
|Era 1 books||Mistborn: The Final Empire · The Well of Ascension · The Hero of Ages · (Mistborn: Secret History · The Eleventh Metal)|
|Era 2 books||The Alloy of Law · Shadows of Self · The Bands of Mourning · The Lost Metal · (Allomancer Jak and the Pits of Eltania)|
|Shards||Preservation · Ruin · Harmony|
|History||Classical Scadrial · Final Empire · Catacendre · Elendel · Southern Scadrian|
|Magic||Metallic Arts (Allomancy, Feruchemy, Hemalurgy) · Metalborn · Mistborn · Misting · Savant · Ferring · Twinborn · Compounding · Atium · Lerasium · Ettmetal|
|Other Media||Mistborn Adventure Game · Mistborn: Birthright · Mistborn film · Mistborn: House War|