The Sword of Dawn is hidden in the Reverce Castle. Remember where you got the double jump relic in the normal castle? Well, to the left of that there's a secret breakable wall. Attack it to reveal a hidden pot roast. But when you're in the Reverce Keep, repeat the process to reveal the Sword of Dawn. Execute this move to summon Dawn warriors: down,forward,then square or Circle. Meanwhile the Great Sword can be easily obtained by defeating a gold Armor Lord in the Reverce Castle. It won't always work though. Keep trying.