Phaaze

When you land on Phaaze, you'll find that the phazon inside of you has become dangerously unstable. You'll have to vent your energy tanks as soon as you land, which will result in a new bar on your screen. You'll permanently be in hypermode while you're here, but you'll need to hurry and find Dark Samus: if you don't manage to reach her before your countdown bar fills with yellow, you'll die. The countdown bar will fill from contact with the atmosphere, and from damage that you take, but you can reduce it by picking up health containers and unloading energy into hyper grapple targets.

Begin by heading into the Entry Canyon. Hopper Metroids will attack you here, but you'll easily be able to defeat them with your hypermode beam fire. Kill them, then overload the phazon plant with your hyper grapple and drop down to Cavern Alpha. You'll need to roll through the next hallway to avoid getting trapped. Use a missile on the growth on the wall here and hop up and through the hole that's created.

Down, Down, Down

Roll up into a morph ball in Cavern Beta Access and start using your hyperball attack on the small plant buds along the pipe. You'll need to destroy all of the small red roots to take out the larger plants that are blocking your progress. When you've destroyed both of them, drop down and let the phazoid puffer here drain some of your excess phazon and reduce your countdown meter before blowing it away.

You'll have some unique challenges to get past if you want to fight Dark Samus here.

In Cavern Beta, do your best to avoid the metroids and jump across to where you can missile the phazon growth. Jump across and blast another growth to reach the door leading to the Drop Shaft. Roll up into a ball here and use your hyper bomb attack to destroy the red growths around the corners of the room. Repeat this process until the center growth dies, then go down and do it again. In the third room, another puffer will be floating around. Let it drain your meter, then destroy it and the growths to move on. When you reach the bottom of the chasm, use the hyperball attack to destroy the monster you fall into.

Metroid Cavern

Roll up into a ball here and drop to the floor. There's a strange organic door at the bottom of the chasm here. If you roll up next to it and hold down the button for the ball attack, you'll eventually overload the door and destroy it and its antennae, allowing you to move on. Next up is another set of metroid hoppers. Kill them until they stop dropping from the ceiling and you'll be able to move on.

When you fall down into the next chasm, you'll be caught by a creature halfway down. Missile or blast it in the mouth to weaken its grip and continue your journey.

Genesis Chamber

Take out the Leviathan Infant to open the path to the core of Phaaze.

When you reach the Genesis Chamber, start scanning everything. The Leviathan Hatcher in front of you has two weak spots on its sides. Grapple them off with your grappling hook to tear it open and have a look at its insides. The Leviathan Hatchling within is tiny, but laden with phazon; if you destroy it, you can destroy the Hatcher itself. While fending off the metroid attacks, keep blasting at the Hatchling; it'll take a while to kill, and will move from one side of the Hatcher to the other, so you'll need some time to completely destroy it.

When it does blow, though, it'll drop a lot of health for you and reveal the passage downward. Suck everything up and drop down to the final boss fight.