In Game of Thrones S08E06, we see
Arya deciding to conclude her character arc in Westeros
and set sail to West of Westeros. Jon asks her what is there in West of Westeros & she replies with something like Nobody knows?
Do we know what lies beyond West of Westeros? Do we have anything to go by from A Song of Ice and Fire Or from A World of Ice and Fire or other supplementary books from GRRM?