The music should swell with the combat, especially the boss sequences. It should give the player a sense of grand scale and adventure. While the player is trekking through lesser populated areas of the desert the music would be a bit more wistful and lonely.
Swishing silk or cloth will be a very important sound effect. Besides that weapons striking enemies or the ground will clang or thud. The titans making a huge cracking or earth shaking sound while they move. They may groan in pain or anguish while you are subduing them.