Teacher's quotation: this is a briefing not a discussion.

About The Dead

Gretta, one The Dead ‘s character, can't be consider a main character because the reader hasn't important informations about she.
Gretta has the narrative function to activate Gabriel's epiphany.
Epiphany comes from a religious festival called Epiphany, it celebrates the journey of the magi visit the baby Jesus who is representation of transformations: God is become man.
So Joyce's epiphany symbolize the inner maturation of Gabriel.

About Tradition and Individual Talents

The sentence has the function to tell the reader what make a writer traditional. He is traditional when he is conscious, aware of his position in time seen under the perspective of temporal (express with this time's language) and timeless (appropriations of old writer's concepts, intuition may be only through Culture).