Lerasium is a metallic form of the god-like entity Preservation,
All known samples of Lerasium were created by Rashek when he took the energies in the Well of Ascension (another manifestation of Preservation) and condensed some of its energies into a solid form. The last existing bead of Lerasium was ingested by Elend Venture roughly one thousand years after Rashek made this metal.
People who ingest this metal gain access to all forms of Allomancy and become mistborn. It is also possible to alloy Lerasium with one of the sixteen basic Allomantic metals. People who ingest this mixture end up becoming a misting associated with the basic metal used in the alloy. Allomancy is hereditary, and later generations will also be capable of this ability, although the powers will eventually become diluted.
Due to the rare nature of this metal, any Feruchemical or Hemalurgic applications are unknown.