In the chandelier room with with the spikes, get to the other side of the room and pull the large metal box once. Walk up the stairs, and get on the ledge to your right. Pull out the boomerang, and target above the left side of the doorway. Now use a Long Jump to get onto the chandelier.
In the second chandelier room, make your way down to the chain you would normally have to pull to raise the chandelier. Pull out the Gale Boomerang, and target above the left side of the door. Now just use a Long Jump to get across the gap.
Head to the left (GCN) in the large room after the Four Poe room. Turn into a wolf, and get by the pillar. Face the acute angle between it and the wall, and press B repeatedly (GCN) to clip through the pillar, and climb up to the Boss Key. This also allows for you to get to the Death Sword battle quicker if you proceed through the door and spinner track room.
After preforming the above trick and making your way to the stalfos room before the spinner, cross the sand and place a bomb by the since stalfos. Now run over to the ledge before the spinning spikes and place another bomb. The stalfos should be destroyed, opening up the gate just before you get there.
After attacking Death Sword as a wolf and causing him to materialize, hit him with the clawshot to aggravate him. Now pull out the Ball & Chain and keep it spinning above your head while Death Sword moves around the room. When he gets hit, move a bit closer to him so the Ball & Chain will hit him. Hit him with it 5 times and then use the clawshot to aggravate him again. Repeat the process once more to finish him.
During Stallord's second phase, knock him down with the spinner, then move close to him and use a Jumpslash - Spin Attack - Spin Attack combo. You want to make sure you're close enough to him for each spin attack to hit him 3 times. Use this combo a total of 3 times to finish him off.