Metroid Prime/Spider Ball

Phendrana Drifts
Now it's time for an upgrade that will open a lot more of the game to explore. The trade off though is there is a rather nasty boss guarding it and there's a tough battle to fight.

Ruined Courtyard
Go to the door across the courtyard from the Save Station and scan it to learn that it needs power just like the one in the Research Core. Scan the metal arch above the door to learn that there is a power conduit here but it's blocked by a Cordite statue. Cordite means you need a Super Missile so shoot one at the statue. Then switch to Thermal and shoot the Wave Bean at the power conduit to power up the door. Now you can go through. (If you already know where the power conduit is then you don't really need the Thermal Visor to get through this door, which means that you can get to the next boss without it. It's a bit of a sequence break but since you need the visor to defeat the boss, or at least it will be very difficult to win without it, it isn't a good idea.)

Quarantine Access
There are Bombus patrolling this passage.

North Quarantine Tunnel
This is a long Morph Ball tunnel with Bombus about midway. There is nothing you can do to get rid of the Bombus so either time your way past them or use Boost Ball to take your chances and power your way through.

Quarantine Cave
The size and shape of this large dome suggest that this is where the boss battle will take place, but there's nothing here but a pile of boulders. Drop down to ground level and a cutscene starts. First a small rock start to move by itself, then the entire pile boulders organizes itself into a giant made of rock. This is the main boss for Phendrana and the hardest one in the game so far.

Thardus leave behind some Ultra Energy so you can recover a bit, and the Spider Ball.