The sections describe meticulous steps on how to eliminate 2.5x more enemies that is mixed in with the next tier ones on a very long mission! The sections describe meticulous steps on how to conduct one of the longest missions and eliminate all enemies for maximum loot.

Note: Another new challenge presents itself in this mission with the armored MEC that guards the main objective!

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The guide is for everyone, but much friendlier to new players. Everything will be explained to be on the same level as those who are the most experienced. The writing will be easy to follow with plenty of screenshots for those who are too lazy to read everything!

Continuing from Advent Blacksite: Part 2:
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The interior "Boss" pod will have the new MEC enemy that is accompanied by 2 Troopers.
Their patrol usually stays within the building but will occasionally go outside in the building's rear double doors.

Note: They often overlap with the EVAC zone enemy pod, which can make engagement more difficult when sighting both.

The armament includes a Mag Cannon, along with mid-range Micro Missiles (Grenade Launcher).
Such mechanical enemy has impressive mobility to force a head-on fight with its long reach. Once engaged, its 2 armor points nullifies most conventional Tier 1 weapon damage.

The enemy has heavy armor that must be shredded first to inflict decent damage.
The Grenadier with Shredder skill or any grenade will shred 1 point of armor.
The Specialist's Combat Protocol attack ignores armor to guarantee 4 damage within sight range. The alternative is the Haywire Protocol and easier with a seasoned Specialist for more successful result of either shutting it down or taking complete control.

Note: Any accuracy boosts should be given to the Grenadier for such purpose.

The Boss pod that guards the Vial inside does not go outside unless making contact through a window. Still, the best way to first engage this pod is for it to walk into an overwatch-ambush so you get a free chance to do some damage. The best place to set up that ambush is at the front factory door, or using a corner tower (see below in the guide).
The optimal approach is to scout with a concealed Ranger first then lure them into an ambush with a correctly positioned Sniper.


Sharpshooters sniping from towers or rooftops still get good odds, though that armor is a problem.

In an emergency, a cloaked ranger has an excellent chance to punch through even un-shredded armor with a critical hit.



While there are many ways to engage the early pods, in general staying on the left rooftop near the end of the train creates the best options for having a clear view/line-of-fire over the train and the freight yard.

The long sniper shot aided by a stealth scout buys you time, because the targeted pod doesn't know where the shot came from.

Be patient. Eventually the pods patrolling the sides of the map will patrol into your overwatch, which gives you the most shots to kill enemies before they get a chance to shoot back.

If you don't have a stealthy scout and you suspect there are nearby enemies, advance only gradually. Remember you don't want to alert them till they move into your overwatch.

Stay out of the freight yard until you are sure there are no more pods that might flank you.

Once you are sure there are no flanking pods left, its safe to clear any turrets overlooking the freight yard. There is no rush now, it might take a while... that armor is tough!

The concealed Ranger can safely open the door to safely locate the Boss pod.

Once the patrolling pod moves far enough back that the rest of your squad can safely move up to within 1 blue-move of the open door without alerting the pod, do so and put them all in overwatch. They don't need to be in cover - the alien pod will move into your ambush during its turn, so you get both an overwatch shot and your next turn to react.
Eventually the pod will move forward into your overwatch ambush...
Hopefully someone gets in some damage, as this makes your coming turn much easier :)
Now that the trap is sprung, blue-move your soldiers directly into the two open door spaces so as to block the exit and focus-down the MEC to finish it off.
It is imperative you kill the MEC in your first turn. Don't worry about the two alien troopers just yet... that is what the door is for ;)
Once the MEC is dead, close the door with a free soldier and finish the turn without moving anyone. Any soldiers blocking the exit must remain there, and the door must be closed when you end the turn.
In your next turn, open the door again... the enemies have re-positioned, but they couldn't get to you (but beware of enemy overwatch), so now they are sitting ducks! Open and close the door as often as needed till they are finished off :D
That one won't be abducting anyone ever again...

Since the enemies can't get through the door, sometimes they will try and run around the outside to flank you... but they don't have enough moves to both move and fire :D
That was their mistake...

Such technique is best when the Ranger no longer has a concealment advantage.
The Squad will still block the doorway in advance before opening the door.
Listen for sound between turns. If you hear something, it means the MEC pod is likely nearby and opening the door now will activate it. So it might be wiser to wait to open the door only when you hear nothing for a few turns.

When you think the coast is clear, open the door to have a look what's behind it. If you are lucky, the MEC pod will be far enough back that it doesn't see you yet, and from there you can put all your soldiers in overwatch, setting up an ambush while leaving the door open.

If you are unlucky, the MEC pod might have been camping silently within sight of the door and activates. In this case, focus down the MEC and kill it using grenades, combat protocol, whatever it takes.
Once the MEC is eliminated, the doors can be safely closed while the Squad is still block the door way and deal with the Troopers on the following turn.

The two guard towers at either end of the freight yard serve as excellent ambush positions.
A concealed Ranger can move along the facility's side windows to possibly spot the MEC.
The Sniper may make an opportunistic attack on the MEC or the EVAC Zone enemy pod.
The advantage is potential enemy confusion due to a very long-range attack.

The extreme angle and potential tree obstacle will create less firing solutions.
There will be no door to block enemy LOS and surviving enemies that are within firing range can do some damage on their turn, especially the MEC with the micro missiles.

Note: The MEC pod has a chance to patrol outside through the rear double doors.

A full enemy pod that consists of 2 Stun Lancers and a Sectoid will guard in this area.
They are difficult to avoid and their patrol often intersects with the Boss pod.

Note: They will follow you when the Squad tries to run past them to reach the EVAC zone.

The Turret can also be randomized to be placed on the roof of the rear double doors.

Their control can offer excellent distraction while picking them off with the Sniper!

A decision needs to be made to not obtain the vial for loot farming with repeated missions.
The mission result will be a failure but have zero penalties incurred when choosing not to.
The equipment loot and XP will be retained for each repeat and can be done indefinitely for even more! ;)

Note: The loot will be more important as XP will be capped at Colonel rank.

Ambush methods to deal with reinforcements are described below.
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The enemy reinforcement composition will be a mix of the three types.
The area near the evacuation zone will randomly light up with two consecutive red flares but limited to one active reinforcement at a time.

Note: The second enemy reinforcement can be skipped, if all soldiers can evacuate beforehand.

The first run of the Blacksite may have some incredibly disappointing loot.
Repeating the mission may be worthwhile because more loot translates into extra supplies!

The enemy composition and their patrol routes will be roughly the same for each mission.
After 1st "failed" Blacksite mission run... Rookie gained Specialist.
After 2nd "failed" Blacksite mission run... new Rookie became Grenadier and 3 Lt promotions!
After 3rd "failed" Blacksite mission run... new Rookie became Sharpshooter and 1 Lt promotion!
After 4th "failed" Blacksite mission run... Squaddie became Cpl, and 1 Cptn promotion! Now I can buy GTS-squad-size II, and it is only April 9th!

After a 5th run, I will certainly have 4 Captains...

Each repeated mission becomes easier after being familiar with the enemy placements.
More detailed description of enemy patrol pathing in certain areas of the Blacksite.

• The 2 Train patrols wander mostly between your start location buildings and the train, but can sometimes detour unseen through the freight yard. Easily ambushed from the rooftops of the buildings.
  
• The 2 Sideyard patrols wander along each side of the map, but they also patrol up to the two ends of the train, so can be ambushed there if you wait long enough for them to show up.
  
• The freight yard patrol is generally stationary or stays near the entrance to the main refinery building, sometimes under the protection of a laser turret (if there is one). You will have to figure a way to lure it to you if you don't want to fight in the freight yard.
  
• The boss Facility pod patrols the large main processing area of green goo. It can be ambushed using sharp-shooters in the corner towers sniping through the windows, or through the open main door.
  
• The last Facility pod (I have also encountered 2 of these) patrols the rear areas of the refinery, 50% of the time pathing outside and 50% inside. They can be ambushed using snipers in the corner towers or on the roof, but the angles are bad for clear shots.

If you move towards the Evac Zone without eliminating the patrols first, the remaining ones will leave their normal areas and tend to gravitate towards your location.
3 pods worth of carnage, from just being patient. A good start :)

Note: The enemy pods become more dangerous as their difficulty scales with the given month.

The Blacksite mission is now complete and its vial can now be researched at the Shadow Chamber!


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