If you go left at the walkway, a Tarydium barrel can be used to blow up two wooden crates, one of which contains a box of 50 Bullets. Beware as you approach the walkway however as part of it will collapse into the lava. Now head the other way along the walkway, where a short corridor on the right contains two Health Packs. Continuing along the walkway another section collapses so watch out.
Tip: If you fall into the lava, follow it round underneath the walkway. A lift will descend and you can use it to get back on to dry ground by the two Health Packs mentioned above.
At the next junction you are faced with a choice; the left path, the middle path or the right path. You can hear a Skaarj growling on the left, so don't go there yet. A Nali can be heard praying to the right, and you don't want to draw him to the attention of the Skaarj as the Skaarj will probably murder him. So instead, take the middle path and follow the corridor. Collect Clips and Tarydium Shards as you go.
Now the SkaarjScout you heard growling may come and meet you in the corridor. Most likely however he will be operating a console and you will find that you come out behind him. Either way, dispose of him quickly without leading him onto the Nali. The console he was operating reads:
"WARNING: Intruder detected in Sections C-6 and D-8. All personnel are responsible for patrolling their local area."
Head now to the left, along the walkway over the lava again, back in the direction of the junction. Collect the Voice Box inventory item as you go from behind a pillar. Now go off to the left, where the Nali can be heard praying.
When you see the Nali, don't shoot him. Never shoot the Nali, because the more you shoot them, or let them get killed, the less helpful all the Nali will be to you as a whole. This particular Nali beckons for you to follow him; do so, but grab Tarydium Shards and Health Packs from the crates first. The Nali will lead you down the middle corridor and will open a secret compartment in the wall, where there will be further Tarydium Shards and a very useful Stinger weapon.
Follow this corridor now to its end, so that you arrive back at the Skaarj's console, and this time make a right. A gap with lava below and a low beam blocks your way; shoot the red plate on the wall over the lava and the beam will rise, making a handy bridge.
Cross the gap, and take out the Tentacle hiding round the corner. Collect the Clip, and select the Stinger. Enter the cave on the right, and you will be greeted by a SkaarjScout who drops in from above. He is best taken out with the Stinger's secondary fire mode. Mercifully now the action music from the first fight has stopped and is no longer doing your head in.
Having disposed of the Skaarj, shoot the tarydium barrels at the far end to open a hole in the wall. Follow the new tunnel - collecting a Health Pack as you go - into the next room where a LesserBrute will greet you. Now, step up to the lever on the left and press it. Buttons will be revealed on the central column. Press all four to open the doors around the room. Doing so will release an angry SkaarjScout whom you should dispose of. The two corridors revealed each lead to the same lift, and each contain two Tentacles and a Clip. Not much to choose really, take either or both. Ride the lift up to the corridor above, being sure to collect the Shield Belt from the alcove at the far end of said corridor.
Enter the next area - balconies over the room below - and grab the Stinger and Tarydium Shards. Dispose of the SkaarjScout lurking beyond the central column. You might also take this opportunity to kill the Tentacle that snipes from a walkway above.