How to Unlock: Approach one of three Remnant structures [Elaaden].
This page contains walkthrough of Dismantled. This is one of Heleus Assignments (side quests) in Mass Effect: Andromeda, which you can start during exploration of Elaaden, right after landing there. This mission involves finding and investigating three Remnant locations scattered across the planet.
Unlocking the assignment
As soon as you get to one of the three Remnant sites, the mission will be added to your journal and start automatically. These sites are hard to miss - the places you need to go to in this mission are perfectly visible even from a large distance, because these are simply huge Remnant structures. The first site is north of the starting point on this planet (Paradise Sands) - the two other show up on your map when you get to the first one.
Investigate the Remnant site
When you get to the site you will notice two spots (Remnant Core), which you can interact with. Before you do that, however, deal with all enemies in the area - there are both Rebels and Remnants here. Then come close to any of the two objects and interact with it. The deactivation process takes a long while, and as soon as you start it enemies will come running. Most of them, however, will not pay much attention to you, so you should be able to successfully deactivate the core.
Now you must clear the area of all enemies, and head to the other core - you may want to consider restoring ammo on your way. As soon as you interact with the second core, another group of enemies appears. As you did before, focus on deactivating the core, and then eliminate all enemies that spawned there.
Investigate the Remnant site (2/2)
Once you have investigated the first Remnant site, two other will be marked on the map. You must travel there (in any order) and repeat the whole process. First kill all enemies in the area, then deactivate the core, deal with another group of opponents and activate another core. After that you must head to the last Remnant site and do all those things once more. Moreover, at one of the two sites there is a Remnant Console - this serves for uncovering one of the two cores, which is hidden there. Once you have deactivated all three cores at all three sites the mission is completed.
Rewards: XP, Andromeda Viability Points.