Leftherians are a race of humanoid in Xenoblade Chronicles 2. They are one of the most recent species in all of Alrest and like most other humanoids they are very similar to the ancient Humans who lived in Alrest long ago.
The Leftherian are a very recent species that was born less than 500 years before the events of the game. It was Addam Origo, the legendary Tornan hero who first colonized the Leftherian Archipelago and created Fonsett Village after the end of the Aegis War. Addam left a lot of artifacts that could only be used by the ones who share his blood. After his death, his descendants stayed in the village and 500 years later, all of the Leftherian shared the blood of Addam, which gave them powers found nowhere else in Alrest.
The Leftherians are one of the two species along with the Tantaleses that shares the heritage of the Tornans after the destruction of the Kingdom of Torna.
Addam Origo - Technically a Tornan but his genetic makeup is what would become the main difference between the Tantalese and the Leftherian. He was also Mythra's original Driver.