Twinborn
A Twinborn is a Metalborn with one Allomantic power and one Feruchemical power.
Notable Twinborn included Waxillium Ladrian, Wayne, and Miles Dagouter.Cite error: Invalid <ref> tag; refs with no name must have content
Twinborn only began to appear after the Final Ascension, due to the intermingling of the Terris people with the others. This mingling also had the effect of diluting Feruchemical power, creating Ferrings. The interaction of Feruchemy and Allomancy in a single person allows for both practical benefits of the power (Bloodmakers healing in a time bubble, Coinshots augmenting their weight with Feruchemical iron).
Compounding
If the Twinborn is fortunate enought to obtain the allomantic and feruchemical abilities of the same metal, they can practice Compounding. This is seen in the case of Miles Dagouter and his extraordinary ability to heal due to being born a Bloodmaker and Augur.
Classification
Just as individuals with only one Allomantic or Feruchemical power have a special name (i.e. Coinshot, Archivist), each combination of Twinborn has one as well. At this time, the only the combination of Crasher, Coinshot and Skimmer is known. However, Wayne claims to know the know the names for each of them.Cite error: Invalid <ref> tag; refs with no name must have content Excluding the God Metals (which are unknown at the time of the Alloy of Law this makes for a total of 240 possible combinations.