UNC: Listening Post Alpha

Listening Post Alpha in the Erebus system is reportedly being attacked by unidentified life forms and is requesting assistance.

Acquisition
You first have to complete Noveria to get the Styx Theta cluster on your map. One way to acquire this assignment is to land on Altahe, as part of UNC: Listening Post Theta and fight your way to the back of the base. There are two terminals in the back, one of these will get you this assignment. Alternately, if you enter the Erebus system first you will receive a distress signal and this assignment will appear in your journal.

Surface
Land on Nepmos and make your way to the listening post. Fight off the first wave, then talk to Lieutenant Durand. She will tell you that this has been happening for the last few days and that the three marines remaining are all that is left out of a platoon of 90. You will need to assist the remaining soldiers in fighting off waves of rachni. You can either run over and activate the generator by connecting the Mako, or drive the Mako around during the next two waves of rachni assault. If you connect the Mako to the generator, it will not be available for you to use during the fight, but the rocket turrets of the base will be activated. You will have to disconnect it in order to drive away.

After a successful defense, one of the marines will say that one of the UAVs has found a hollow space about 500 meters below the surface. Lt. Durand will ask Shepard to check it out. She will also mention that another listening post in the cluster went silent a few days ago. Choose your answer, then head over to the mine to clear it out. Before you leave, grab the med kit from one of the shacks, and an upgrade kit and another med kit from the other.

Rachni Infested Mine
Head down the entrance tunnel to reach the first room. When you reach the first room you see some holes on the far wall, but nothing will come out of them. Before entering the tunnel to the main room there is a crate off to the right of the entrance. This is a good point to save the game because of the amount of rachni you will enounter in the main room.

When you enter the main room there will be rachni holes, eight to be exact around the main room. Each of them will only release the rachni when you or your squad get close to them. When you enter the room watch your right because there will be a hole there. It however will only release one soldier. The remaining holes will release two or three Rachni Soldiers. Make sure to get all the holes before heading to the tunnels in the back of the room. There are three crates aound the main room, make sure to find them all before leaving.

This is again a good save point because you will face Rachni Soldiers and Rachni Brood Warriors. Remember that the Brood Warriors have some biotic potential and use stasis and a form of barrier to defend themselves. However the Brood Warriors will come out last. You have to go into the room, i.e. out of the tunnel, in order to get the rachni to come up from their holes.
 * The left tunnel has at the bottom four Rachni Soldiers and one Brood Warrior. Once you kill two or three of the Rachni Soldiers, the Brood Warrior comes up. Before heading back up grab the crate in the room.
 * The right tunnel has only half the Rachni Soldiers at two, but will still have the Brood Warrior. Once you have killed one of the Rachni Soldiers, the Brood Warrior comes up. Grab the crate at the end of the room before you leave.

Take them both out to complete the assignment.

Enemies

 * Rachni Brood Warrior
 * Rachni Soldier

Trivia

 * This assignment may pay homage to the book/movie Starship Troopers.
 * No experience is given for the actual killing of the rachni during the waves. This may or may not be a bug.
 * There also seems to be a bug where Shepard or the teammates 'float' quite far above the ground when near the Lt. Durand or the other alliance soldiers. This is easily fixed by moving far away from them- Shepard will harmlessly 'fall down', and the team-mates will teleport to Shepard's side.