Xeris is one of the vassal realms of Ephedia. The royal family of Xeris were important in Ephedia. The powerful Ancient Ephedian Spell Book was entrusted under their watch. The members of the ruling family were also famous because of their strong magic. Izira was already popular in Ephedia before the start of the series. The same can be said to Talia as in "To Find a Princess", Praxina exclaimed "Talia, the famous princess of Xeris" indicating she made a name for herself even before meeting Iris. However due to some circumstances the royal family was defeated when Gramorr attacked and palace ended up in ruins.
Izira's liberation led to the formation of the resistance. The palace of Xeris was used as their base of operation.
The royal family of Xeris are trusted with Ephedia's knowledge. The were tasked to guard the Ancient Ephedian Spell Book and it's dark counterpart, the Zanevian Book of Spells. Talia seemed to have brought an entire library in their base full of other spell books. Of all the princesses, Talia is the most knowledgeable be it spell or ephedian history and legends.
As of the finale, when they found out Izira managed to escape from the prison, she made a resistance stationed at Xeris.