Crater Entry Point
There is a Save Station close to you, and it's the only one in the crater. As you go through the door, you'll probably notice that this place isn't blue like you might expect, but orange. The orange Phazon is twice as contaminating, and even the Phazon Suit can't handly it.
Crater Tunnel A
Lumigeks, Phazon-consuming lizards, will swarm toward you. Use the same tactics as with the scarabs and parasites. Jump across the Phazon and head through the door.
Phazon Core
A large room with an 'island' surrounded by Phazon. A tower-like structure connects the bottom to the top, and you must climb it. The Phazon also continuously produces a new type of Metroid: The Fission Metroid. This metroid splits in half when damaged a certain amount. The color that the smaller "half metroids" have tells its weakness. Yellow means Power Beam, Red means Plasma Beam, et.c. You must use your expert platforming skills to navigate from one floating platform to another. One wrong move will land you in a large pit of Phazon. Half-way up you will find a door that leads to the Crater Missile Station.
Use the station to get a break from the extremely persistent Metroids. You're gonna need all the missiles you can get for the upcoming fight. Continue up and through the door.
Crater Tunnel B
A straight tunnel. Use the Spider Ball tracks to avoid the Phazon. Behind the door lies the fight that will determine the fate of Tallon IV
Phazon Infusion Chamber
As the door locks behind her, Samus sees what looks like a humongous head hanging from the wall. It soon unfolds into the arachnid-ish Metroid Prime, the source of Phazon. After staring down Samus a few seconds, it breaks down the wall and makes off to a more suitable fighting area. Samus runs after it and jumps down to the fight.
Metroid Prime
The gigantic Prime is a devil to take down. The veins on it's carapace will change color depending to which beam it's vulnerable to, similar to the Fission Metroids. However, each color gives it a powerful corresponding elemental beam attack. Yellow beam will knock out your Arm Cannon, Wave beam will cause severe static to your visor, Ice beam which will freeze you, and Plasma beam that does more damage than the rest. Other than these, the attacks it will do regardless of color are biting you, slashing you, running you over, releasing homing orbs towards you and freezing the ground in a straight line towards you. Sometimes, it will grab you with a grapple-like beam and drag you towards it. When it does, immediately turn into Morph Ball and roll in the opposite direction until it lets you go. Prime will sometimes attempt to trample you, so Morph Ball into the nearby ditches to avoid it. Throughout the battle, Prime will flee deeper into the tunnels as it takes damage. Eventually, it is beaten and falls down a large shaft, but the kill is not yet confirmed.
Metroid Prime Lair
Essence of Metroid Prime
Samus jumps down the shaft and finds a large, circular room with blue Phazon about. Opposite of her lies the broken body of Prime, but it's not finished yet. A blue, transparent and octopus-looking entety floats out of the shell and attacks. All weapons are now deemed useless but one. That weapon is the previously unusable Phazon Beam! But you can't use it wily-do! To use it you must wait for True Prime to produce a ultra Phazon pool, but producing Metroids as well. Upon stepping in the pool, your visor blurs a bit and it says "HYPER MODE". Unleash all out doom to True Prime. Do this quickly! The pool doesn't last forever! Now, this doesn't mean True Prime is defenceless! It has many powerful moves. Move One: Whip. Hit you with tentacles. Back off. Move Two: Camo. Disappears. Use Thermal/X-Ray(one works one time, maybe again) to see it! Move Three: Summon Metroids and a Phazon Pool. Depends on heath. Summons regular, Humter, or Fission. Move Four: Spin Whip. "Back Off!" move. You SHOULD back off. Move Five: Ram. Self Explanatory. Side Strafe to dodge. Rarely used. Keep fighting hard and you should win. If you lose, too bad! The end movie depends on items collected. I'll leave you to find all three out.