3rd Omega Metroid

Walkthrough: Return to the tall room on your right, opening the door at the bottom with a charged missile. From there, use a Power Bomb to open the small hole you find. Head upward toward the Aeion Recharge Station, collecting the Missile Expansion on your way, and then open the door on the left before continuing to the right. You should quickly come to a door that contains the third and final Omega Metroid of Area 7. Defeat it, and then head back to the Chozo Seal.

Drain the purple lava once you reach the Chozo Seal, and then start heading downward. The first door you find will have a Missile Expansion, the next will have a puzzle that leads to an Aeion Tank. After those room at the bottom, begin heading upward and use a Bomb to the left wall. Roll up and pull on the red orb you find. Go back a little ways to use the new passageway to continue heading upward. Screw Attack through the two floors, and then go left and use the next elevator to reach Area 8.

Missile Expansion #1: Just before the Aeion Recharge Station, shoot a Missile at the weak spot on the wall to the right to find this Expansion.

Missile Expansion #2: After draining the purple lava, drop down and use a Power Bomb near the first door to reveal an opening from above. Use your Phase Drift to make it past the breakable floor, straight to this Expansion.

Aeion Tank: After you drain the purple lava, head down and through the door. In the first room, use your Screw Attack on the floor. Drop down below and pull on the red orb to your left. Head back up and enter the following room on your left. Screw Attack through that floor and then Spider Ball back into the previous room. Shoot a Missile through the slit you'll see, and then pull on the second red orb. Return to the previous room and shoot a Missile at the block that has reappeared. Quickly hop inside and do the same thing again, shooting a missile and then pulling. Exit with a weak spot with one of your Bombs, and then head through the hole you made down to the floor below. The should lead you to the Aeion Tank.