Horizon is a Mission in Mass Effect 2Horizon is a Human colony that has been attacked by the Collectors. Missions in Mass Effect 2 need to be completed in order to progress the story forward, and unravel the mysteries about the Reapers.



General Information


Video Walkthrough

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NPCs in the area


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Key Items

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Full Horizon Walkthrough

Getting Ready

After acquiring Garrus, Jack, Mordin and Grunt (It's not necessary to wake him up), you won't be able to select a new destination for the ship. Kelly Chambers and Joker will inform you that the Illusive Man wants to have a chat with you, if you access the Galaxy Map. Go to the FTL Room, and talk to the Illusive Man.

If you have both Kasumi Goto and Zaeed Massani DLC, you can also obtain them before acquiring the four mandatory teammates to obtain this Mission, allowing you to have as many as eight members to tackle this Mission.

Once you arrive at Horizon, the Mission will begin.


The walk with the Illusive Man will give you information about the situation on Horizon, and you decide to go there in order to save the colony. After talking to the Illusive Man, you will go to the Tech Lab to talk to Mordin to ask him if he has developed a countermeasure to the Seeker Swarms. He will respond affirmatively and show you the schematics.

Before your arrival on Horizon, you learn that the Alliance has recently fitted the colony with GARDIAN laser turrets to defend it. However, the turrets could not be calibrated correctly, and the Alliance decided to send either Ashley Williams or Kaidan Alenko to get them working. Who was sent, depends on the decision during Virmire in the previous game.

The Collectors attack Horizon after establishing a communication blackout. Either Ashley or Kaidan will be talking to the Lilith, one of the colonists, the Collector Cruiser drops into the atmosphere, releasing the Seeker Swarms. Your former squadmate will try to provide cover, but will end up getting stung and incapacitated.

Once you land in Horizon, you will find the Collectors moving colonists into their ship. You have to stop them before they manage to get away. Mordin will say that his countermeasure against the Seeker Swarms may not work because it hasn't had a field test yet. Keep going, round a corner and engage the Enemies.

Keep behind cover, move around and take down the Collectors. Don't rush forward, as reinforcements will arrive by air. Once you have dealt with the Collectors, pick up the Heavy Weapon ammo in the middle of the area, where the Collectors were. Hack the datapad on the picnic table to obtain x6000 Credits and then head down the path.

In the next area you will find several buildings and more Collectors harvesting Humans. Take cover quickly and deal with them. There are also Husks present, don't let them get near you, try to take them out before they rush you. You can use the buildings on either side to flank the Collectors with your teammates. Once you have cleared the area, enter the building on the right to obtain x4200 Credits from a datapad. Outside said building, you will find a dead Collector, that you can scan to obtain a Heavy Skin Weave upgrade.

You will find a dead husk around the corner, you will see a cutscene where Commander Shepard notices the difference between these Husks and the ones on the previous game. At the end, the team rallies and then move on.

Enter the next area slowly, and put your squad in cover. Run up the stairs from where you enter to bypass a wall safe to obtain 4800 Credits and Medi-Gel in the building to the left.  Move into cover and face the Collectors, as you did previously, try to flank them using the buildings to your advantage.

Once you defeat them, do not go past the pods or where the paths narrow, because that will cause more Collectors to spawn. Move around this area to collect items and Equipment. There is a med kit in a building to the left of where you entered. From that building, move across to see some colonists in stasis on some stairs. Take those stairs up, to find more ammo and a computer in the room that can be looted for x3000 Credits. Going down, look in the center of where you just fought to pick up the Collector Particle Beam Heavy Weapon. Doing so will replenish your Heavy Weapon ammo if not full. It is advised to save your game here, and go beyond the choke point.

As soon as you go beyond the choke point, more Collector troopers will arrive, and you will see a short cutscene. You will encounter Harbinger for the first time. He will assume control of other Collectors and direct the battle. He is no pushover also, he possesses barriers, armor and powerful biotic attacks. He can possess one Collector at a time, so once he does, target that one to take him down quickly to then refocus on the other ones. Once the battle is over, move around and recover the power cells. You can find them in a building to the west. There's also a computer to the north that contains x3000 Credits. Now head to the large doors to the south and bypass them to enter the structure.

Move inside and eventually you will find Delan, the local mechanic. He can tell you about the attack, where your former squadmate is, the towers that were installed and his anger at the Alliance. You can earn some morality points as well. You reach the conclusion that the GARDIAN laser towers are the key to destroy the Collector Ship. He will point you to the spaceport to get the towers operational.

Use the Weapons locker in the garage if you want to change your loadout. There's Platinum, Medi-Gel, and 6000 credits to be obtained from the wall safe. Save your game and leave the garage.

There isn't much cover in the next area. As you get close to the edge of the wall to the right, move into cover and try to position your teammates where you can cover them. You will find Collectors, Husks and Scion. Harbinger will also make an appearance sometimes, so don't forget about him. If Harbinger or Scion, is about to come around the wall, run back to the large piece of farm equipment.

Once you have dealt with all the Enemies, move around and collect the clips they have dropped. You can find some power cells on a walkway to the left of the entrance and a computer that can be looted x3000 Credits on the upper level. On the right, you can find a dead Collector that yields a Hyper-Amp research upgrade. Once you have picked up everything, head to the doors of the Starport. Save again, then bypass the door to enter the Starport.

Move to cover and be prepared for a Husk mass attack and two Scions. Take cover, use melee attacks and powers to take out the attacking Enemies. After one Scion is dead, head to the other side of the staircase to defeat the second one. If you manage to defeat both of them without being detected, the Husks won't be spawning.

Once all the Enemies are gone, don't go to the transmitter yet, you can find a crate of Heavy Weapon ammo to the far right. On the opposite side, you can find a med kit. After grabbing all the items it is advised to SAVE YOUR GAME,  then hack the transmitter. You will ask EDI to realign lasers and bring them online. This is not an automatic process, and it will take time, so you have to defend the tower while the lasers charge.

You are about to face a really difficult fight. Enemies will attack you from multiple sides and they will come in three waves. The first one consists of two Husks, a Collector Assassin, a Collector Guardian, several Drones and Harbinger. The second one is composed of a Drone, a Guardian and Harbinger. The last wave consists of four Husks, a Drone, an Assassin and Harbinger.

Try to take the fight as far as possible to where the Collectors arrive. The first two waves will enter on the far side of the area, opposite the doors. So it is a good idea to position yourself towards the door side. Harbinger usually advance towards your position or try to flank you, the other Collectors not as much. 

Try to stay mobile and focus on the Husks first. The Collector Guardians will deploy temporary shields to protect hostiles, so try to flank them rather than shooting through it. After one wave is down, move around to combat the next, but don't stay in one place for too long, because you will eventually be flanked and taken down. 

After the second wave, there is a brief pause, this allows you to head to the far end of the area opposite from where you entered through to change position, because this final wave, spawns near the entrance door. Again, first focus on the Husks and then start taking down the Collectors one by one. 

Once the laser reach 100%, EDI will come over the comm to tell you, but this is not over yet. Harbinger will bring the Praetorian to the fight. Although deadly, the Praetorian is by itself during the fight, so you don't have to worry about any other Enemy. The Praetorian has two deadly attacks, Death Choir and the particle beams it fires from its eyes, and it has two levels of defense, Armor and Barriers. 

When you break its barrier, try to damage it as much as possible because it will perform its Death Choir attack. It glows and slams the ground. If you are too close to it, it is game over. This attack has a shockwave that will penetrate cover as well, so the only way to be safe, is by being far enough away.

When the Praetorian glows on the ground, don't shoot it because it won't do any damage to it and you'll be wasting ammo. Everytime you are out of its sights, try to revive teammates, search for ammo, or reacharge shields and health. Keep repeating this until the Praetorian is done.

Once the fight is over, the GARDIAN towers will force the Collectors Cruiser to retreat and you will meet your former teammate. If you had a romantic relationship in the previous game, the reunion with your former teammate will play a brief cutscene, but learning that you are working for Cerberus breaks the mood almost immediately. Your former teammate went to Horizon because the Alliance received a tip that is was the next colony to get hit, but also to learn if Cerberus was behind the attack on the colonies. You see either Ashley or Kaidan incredibly upset about your allegiance to Cerberus and refuses to join you. After this conversation, and learning what has been happening these last two years while you were dead, you automatically return to the Normandy.

Inside the Normandy, you get automatically in communication with the Illusive Man, who is extremely satisfied with the results on Horizon. You however, aren't as satisfied with him because of the information that leaked you are allied with Cerberus. The Illusive Man tells you he lured the Collectors to Horizon, and with this, he confirmst his suspicions that they are only after Humans. He states that he will use all his resources in finding the Omega 4 Relay, while prompting you to keep building your team, and hands you three more Dossiers.




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Trivia & Notes

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