i'm horribly new to the game and don't even know what an epic phase is

Lucky for you nobody uses em so you dont need to

Any good cards in it though?

The Bastard of Godsgrace slots well into almost every Martell deck.

Some people use epic battles, most notably Stark Siege of Winterfell decks, and Baratheon rush melee decks. The others, not so much. The only location in that pack that really sees any play is Claw Isle, but those reducer locations can be helpful in thematic decks (Night's Watch, Wildling, and Lanni Clansman).