Calla

Calla ​is an unseen character mentioned in the fourth season.

Background
Calla is the seven-year-old daughter of Master Mighdal, one of the Great Masters of Meereen. She was tutored by a slave named Fennesz before Daenerys Targaryen abolished slavery in the city.

Season 4
When Fennesz explains his background to Daenerys Targaryen, he mentions that Calla has come to admire her after learning about her family's history and her accomplishments.