Castellio「カステリオ Kasuterio」 is a kingdom located within Britannia.
Not much is known about this kingdom, but at some point it was destroyed
The Kingdom of Castellio was briefly seen in Escanor's flashback that resulted from Gowther's Nightmare Teller. There, Escanor reminisces his childhood where he remembers being bullied by his older brother Daymond before subsequently awakening his power Sunshine and breaking Daymond's arm. Declared a monster, Escanor is chased out of the kingdom and, aided by Rosa, manages to escape across the sea in a barrel.