This is the mission that Wreav (or Wrex) will have given you earlier on the Normandy. He will ask that you investigate a missing turian squad, one of the finest of the species. They have disappeared startlingly close to Rachni territory, and the krogan diplomat will insist that he suspects the Rachni, although the species has been long extinct, especially if you killed the Rachni queen in the first Mass Effect. It is now your job to head to the Rachni Relay and rendezvous with Aralahk Company, another krogan squad. From here, you will seek out the missing soldiers in the planet’s cavernous ruins.

When you land, you will have a brief conversation with Urdnot Grunt (unless Grunt died in Mass Effect 2, in which case Urdnot Dagg will appear here,) the leader of Aralahk Company. After your conversation, search the camp before doing anything else. Pick up the M-300 Claymore to the left, the Pistol High-Caliber Barrel Mod, and the Spare Parts to the side. Head further down the path to reach a small clearing with a building, where Dagg will be waiting. Search the building to find the SMG High-Caliber Barrel Mod, a weapon bench, and Spare Parts outside. Speak with Grunt to proceed. Walk into the building next to him. As you do, the ground will give way and you will plummet into the caves below.

Head forward and pick the M-451 Firestorm Flamethrower up from the dead soldier ahead. Use it to burn down the strange webbing that blocks your progress ahead. Keep following the narrow cave path, burning down the webbing where necessary, until you come upon a group of egg sacs littering the ground. Burn them from a distance and watch them explode. Let this be a warning to never get close to the strange eggs, as they will explode when you near them and damage you heavily.

When you enter the next area, through several more of the strange webs, you will encounter a group of enemies. A strange, bulbous spider creature is the main threat here. This is a Ravager, and it is most definitely of Rachni origin. The Ravager will maintain its position at the top of the cliff, while tiny enemies and Husks will swarm over you to distract you. The Ravage will shoot powerful projectiles in your direction, so be sure to take cover whenever you see the telltale beams, side by side, aiming from the creature’s head in your direction. Order your squad to take cover directly in front of the Ravager, so that it will focus on them. Keep low, and sneak around to the right. Run up this curving ramp, behind the pillars, which will shield you from the Ravager’s view. The twisting ramp will lead you directly behind the Ravager. Torch it with the Firestorm. If you no longer have the weapon, use Incinerate, Biotic Charge, Carnage, a Shotgun, or a charge melee attack to deal heavy damage from close range. If you lack close range skills, you will have to take a more measured approach, holding back in cover and picking off the Husks before killing the Ravager.

Grab the Firestorm from the dead soldier at the base of the ridge where the Ravager sat. Use it to burn through the webbing in the back of the room and continue onwards. Burn the egg sacs and the next web, and you will soon reach a tall obelisk blocking your path. Head to the right to find a Reaper Node, a purple device that sends power to other parts of the caverns. Destroy the node to remove the obelisk from your path, and run down the newly opened corridor. The cave will collapse behind you as you walk in, ensuring that you must find an alternate way out after all is said and done.

The path will split into two ahead of you. Both sides lead to the same place, but take the right-hand path to avoid most of the numerous egg sacs that sit on the upper side. When you arrive on the other side, burn through the webbing to the left to reveal some Reaper Tech. Keep hugging the left side of the wall and burn the next webbing as well to collect a note off of a krogan’s dead body. This note will allow you to complete a side mission on the Citadel. Drop down into the next corridor. The upcoming battle will be the biggest in this level, so get ready to fight.

A combination of Ravagers, Cannibals, and Husks will emerge and begin to attack you. You will have two opportunities for flanking them in this narrow area. The first is directly ahead. Order your squad to take cover to the right and focus their fire on the Ravager, distracting its powerful fire from you. Head forward and to the right. The Reaper forces will try to block you off here. Take them out with a Shotgun or Biotics before continuing past and to the left. You will be able to loop around the side of the Ravager here, and hit it with a similar combination of Biotics and ammo that you used to defeat the last one. This tactic works well for Soldier classes, as they can power through the oncoming waves of Cannibals and Husks to reach the Ravager quickly. An alternate way to perform this strategy is to send your squad into the fray with you, but to keep them off to the side so as to distract the Reapers while you sneak up on the Ravager.

Another strategy for flanking is to take the path to the right that you would have had your squad take cover at in the last strategy. Curve up and take cover on the ridge to get a better view of the battlefield. From here, use a Sniper Rifle or a scoped SMG to look down upon your enemies and rain fire upon them. Kill the Husks first, as they will inevitably rush your position, and follow it up by killing the Cannibals in quick succession. Be sure to watch out for the small beam that indicates the Ravager’s line of sight. If it catches you, you are sure to take lots of damage. Kill the Reapers, weaken the Ravager’s shields with Biotics, and use your Sniper Rifle to destroy the creature.