Lerasium is one of the two god metals. A normal person burning lerasium becomes a Mistborn. A Misting or Mistborn burning lerasium drastically increases their powers. Feruchemists can use lerasium to store an unknown quality, and when used as a Hemalurgic spike, lerasium steals an unknown quality.
Lerasium is notable as it is the condensed power of the Shard Preservation. The only known source were beads found at the Well of Ascension. Presumably, the name "lerasium" is inherited from Leras, the name of the original holder of the Shard Preservation, just as the name "atium" is inherited from Ati, the original holder of the Shard Ruin.
Allomantic Use
For normal people, burning lerasium forges a permanent connection between them and Preservation, turning them into a very powerful Mistborn. However, turning people into Mistborn is only a side effect of burning lerasium; if a Mistborn were to burn it, it would have a different, as of yet, unknown effect.Plantilla:Annotation ref
Alloys of lerasium have the side effect of turning those who burn them into Mistings of the metal lerasium is alloyed with. The primary effects of lerasium alloys is also unknown.
Feruchemical Use
Lerasium, when used by a Feruchemist, has unknown properties.
Hemalurgic Use
When used as a Hemalurgic spike, lerasium steals some unknown trait or quality.
Theories
It is theorized that if an Allomancer were to duralumin-burn a piece of lerasium, it would produce a Mistborn of such amazingly vast power that they would be nearly unstoppable. This is as of yet unconfirmed.