You've now explored a good chunk of Torvus Bog; now it's time to explore the Dark side of it.
Return to Torvus Temple and get to the lower part of the room if that's not how you got in. If you're in the upper part, then scan the Emerald hologram to activate the lift if you haven't already.
Scan the door with the Emerald hologram to open it and go through the door behind it. This is the door on the right if you're coming from Temple Access.
There is a Grenchler here and it can be an awkward fight since it's tricky to get around behind it in close quarters. Before moving on, switch to Morph Ball and roll under the ledge at the entrance for a Missile Expansion.
Continue to a part of the passage with a low ceiling and switch to Morph Ball to get through. When you come out there are Sporbs waiting, so quickly switch out of Morph Ball and use Missiles on them. Get the history scan here and use the White door.
Cross this room and just before you reach the opposite door a new type of Pirate attacks. They are Pirate Commandos, the Light version of the Dark Pirate Commandos you may have met before. When you defeat them, the opposite door is unlocked so you can get through.
Use the portal here. There is a platform moving around in the distance, but it's another teaser since you can't reach it until late in the game.
Dark Torvus Bog
There's nothing here but the portal so go through the door.
Hunter Ings, a new type of Ing, are waiting for you here. Shoot them with the Light Beam, but only when you can get a target lock since otherwise the shot will just go through them. Follow the trail of platforms and ledges that circle the central "tree" to reach the Black door.
There is a save station here and it's a good idea to use it because a boss battle is coming. Be sure to hop over the poison water as you come out. Continue up the ramp.
Dark Forgotten Bridge
This is a passage on one side of a room you've been to before, but you can't get to the main part of the room, at least for now. Defeat the Lightflyers to create safe zones here.
Dark Arena Tunnel
Switch to Morph Ball and start across the long series of disappearing blocks. There is no way you can get all the way across without falling through, but you can jump out at the other side. You won't be able to get back once you do though, which is a sign that you'll be getting a new ability soon.
Dark Torvus Arena
As you step into the room you get a short view of a large Ing which turns into a Morph Ball and escapes through a tunnel on the far side. Drop down from the ledge and recover your energy in the safe zone, then follow the Ing into the tunnel. You meet the Ing again and a battle begins.
Grab the refills the monster drops, then get the Boost Ball upgrade it leaves behind. There's still no safe zone here so get back to the one in the main part of the room and recover.
The first thing to do with the Boost Ball to get the key from the wall. The room here has a U-shape which the game calls a half-pipe. If you've played Metroid Prime then using the half-pipe will be familiar, if not it's still pretty easy and you can practice while you're recovering in the safe zone. Roll to one side of the U, then start a boost and roll back, releasing the energy just as you pass the lowest point. If you did it right you should go a bit higher this time. Start another boost and release it at the lowest point going the other way to go even higher. It's best to just let gravity and the boosts do the work, so don't use the control stick. Also, start the next boost as soon as you can after a release; that way you should be up to full power on the next swing. Keep pumping this way and you can get quite a swing going. Note that the camera positions itself to give you a good vantage point for this.
If you start in the middle the half-pipe swing should take you to the key. Once you've gotten it, do the maneuver again starting closer to the exit so you can reach the ledge and the exit.
Dark Arena Tunnel (cont.)
Now that you have the Boost Ball you can zip over the disappearing blocks before they go away, allowing you to get back. Continue on to Dark Falls where you might want to save your progress.
Expansions (Torvus Bog)
The next upgrade is in the Temple Grounds, not Torvus. But there are some expansions to collect as long as you're still here.
Get back to the portal and return to the Light side, then continue back to Torvus Grove. Look for the half-pipe near the entrance to Underground Tunnel and use it to reach the ledge above. Follow the ledge around to the right and go through the Black door.
Get a scan of the small creatures here, then continue to the next room.
This is a side passage as in Dark Forgotten Bridge, scan and use the Spinner here to open the doors and connect the two parts of the room. This opens the doors in the Dark side as well. Then continue to the end of the side passage and blast open the Missile door at the end.
Switch to Morph Ball and start to explore the maze here. The idea is to the reach a bomb slot to change the configuration, which then allows you to reach the next bomb slot. This changes the configuration again so you can reach a tunnel in the middle. Go through to find a half-pipe within a Morph Ball maze. Boost up to the ledge on the right to get a Missile Expansion, then go back.
From here you can continue on to another room, but this turns out to be a dead end for now, so go back to the Forgotten Bridge.
Forgotten Bridge (Cont.)
From the side passage, drop down to the small ledge under the door to the main part of the room, then jump to the ledge on the right with the portal.
Expansions (Dark Torvus Bog)
Dark Forgotten Bridge (Cont.)
Jump to the ledge near the side passage, then to the bridge and blast open the Green door there.
Get a scan of the platform with a crystal in the middle, then shoot it with the Light Beam to raise it so you can reach the Morph Ball tunnel. Follow the tunnel to the other half of the room and get to the exit.
There are a few things going on here, but some of them, such as the key on the wall, you'll need to come back for later. For now, just get to the other side of the room and blast open the Red door.
Save Station 1
There is a save station here if you want to save. Go back.
Venomous Pond (cont.)
Go through through the White door.
Dark Torvus Temple Access
Switch to Morph Ball and follow the tunnel.
Dark Torvus Temple
This is where you place the keys to get to the Dark Temple, but you only have one of them so far. Start by going through the door on the left; you need to switch to Morph Ball to reach it.
As you might of guessed, there is an Ammo Station here if you want to top off your ammo. Go back.
Dark Torvus Temple (cont.)
Now switch to Morph Ball and follow the tunnel opposite where you first came in to a Green door; blast it open.
Grab the Energy Tank that's sitting there and go back. Continue on to Venomous Pond.
Venomous Pond (cont.)
Go through the Black door in the corner opposite the White door.
Switch to Morph Ball and follow the tunnel. There is a door at the other end but it's a dead end for now, but locate the ledge near this door and jump up, switch to Morph Ball again and follow another tunnel to the main part of the room. Use the portal here.
Portal Chamber (Light side)
This section of the room was seen as a teaser before, but the only way to get here is through the portal. Get the Missile Expansion and use the portal again to get back.
Portal Chamber (cont.)
Use the elevator in the corner to get back to the upper tunnel and drop down to the section near the door. Continue back and leave the bog.
Expansions (Agon Wastes)
There are two more Missile Expansion in the Agon Wastes which we'll cover now since they're available, but you may want to wait until later since it may be on your way then.
Get back to the Transport Center and notice there is a half-pipe here as well. There are ledges on either side; one is fairly low and easy to reach with the Boost Ball, but the one you want now is high and difficult to reach. It can be done though if you keep trying. Once you reach the ledge, use the portal there.
Crossroads (Dark side)
There is a Missile Expansion sitting here, so grab it. Note that even though there is a half-pipe here, the ledge sticks out a bit so you can only reach it using the portal. Get to the Light side via the nearest portal.
Make your way to Sand Processing and position yourself about half-way between the pile of sand and the wall in the front of the room. Switch to Morph Ball and the camera should automatically position itself on top of the sand pile pointing to the front. Boost up to the ledge on the left; you have to be between the sand and the hole on the right to make this work. When you reach the ledge, stay in Morph Ball form and hop into the tunnel, then follow it to the control room. Activate the bomb slot there to blow all the sand away and reveal a Missile Expansion that was sitting underneath. So exit the control room the way you came in and grab it. Note that with the sand gone, you'll need to boost up to the back ledge to exit to Save Station C.
The next upgrade is in the Temple Grounds, so head back there.