The Twilight Realm is where Vatti and Dark Link made residence. Its alternate world is the prosperous kingdom of Hyrule. Vatti uses this realm to make plans to destroy the Links. Vatti and his minions lives here. It is actually the Dark World from A Link to the Past, but this flash series named it the Twilight Realm. It is where Princess Zelda is kidnapped. The way to get here is with the use of a Magic Mirror, or a portal hidden in The Cave of No Return.