In this room you’ll find a few Poes. Defeat them and fly over to the other end, but don’t use the door. Instead, use the Deku Flower and fly south then put on the Stone Mask. This will help you avoid the Death Armos.
The "normal" way to defeat them is by shooting them with a Light Arrow to flip them upside-down and then running near them and watch them smash their heads in … it’s much easier (albeit less exciting) with the Stone Mask .
Go to the far end and place a statue on the switch to extinguish the flames around the nearby chest. Collect Small Key #4 then exit the room near the second Deku Flower to the east.
Start off by shooting an arrow into the Spike Mines so they collide and explode. Now use the Deku Flower to fly into the northern passage. From here, fly east and enter the next room.
This room has some Blue Bubbles, just defeat them and enter the next room. Gomess is a mysterious foe that surrounds himself with bats. He attacks with a scythe in a slashing motion, it’s easy to side hop around.
Lock on and avoid the initial attack then fire a Light Arrow . This causes the bats to fly away and reveal the core of Gomess. Hit the core and be ready to dodge,
Gomess will spin the scythe rapidly like a propeller and rush you. Side hop this attack and fire another Light Arrow and strike the core again. Do this a few times to defeat him.
Go through the newly opened door and claim the Boss Key from the chest.