(It's more fun to go into this mission blind)
This mission is the final mission in the game and will determine if the world is saved from the alien menace or if humanity is to become extinct.
Starting Operation Endgame
To unlock operation Endgame, you must first capture a praetor from an alien battleship or a large alien base. Doing this is extremely dangerous due to the elite alien soldiers and the aliens' ability to mind control your men. After a praetor has been captured alive and has been interrogated, you will have the option to research "Operation Endgame". Once it has been researched on the top center of the geoscape screen you will see the text "Operation Endgame" and if you click on it the mission will begin.
Before embarking on the final mission, you should select your best soldiers and equip them with the best equipment available. Don't be afraid to build some equipment if you have the resources at hand.
Operation Endgame has only one objective: to board the Dreadnought and kill the High Praetor. This is a simple goal but it is made extremely difficult because of the guards that stand between you and the High Praetor. These guards range from alien leaders and officers to elite soldiers. In addition to these guards there is a time limit. Once the aliens notice you (which is immediately,) Reapers will begin climbing up from the lower decks towards your crew. If you take too long you will be swarmed by reapers and have no chance to kill the High Praetor or escape.
You will encounter Androns, Caesans, Sebillians, Harridans, Reapers and the High Praetor on this mission. The Sebillians will be found near the docking bay entrance to the deck and will be the first enemy encounterd, they will also be found guarding the two power cores Androns will also be defending the power cores and be blocking your path to the High Praetor. Sebillians will act as the main guard and be found all along the main hallway. Harridans will be found in limited number acting as deadly sniper support.
Reapers will being to appear after a certain interval near the docking bay, they will appear in never ending quantites.
The secondary objective is to save your squad of xenonauts. In order for the ship's escape pods to be activated you must destroy the two power cores. These power cores are well guarded and are a detour from your primary objective. If you wish to save your squad you will risk not being able to kill the High Praetor before the reapers swarm in thus dooming humanity.
If you chose to focus on killing the High Praetor, and ignore the power cores, you will not be able to go back to the power cores. Six Reapers will spawn from the docking bay every turn, the mass quantity of the Reapers will simply overwhelm any attempt to push them back.
(This walkthrough is how to save your squad as well. You can just go past the reactor rooms and kill the high praetor to win the mission however your squad will be sacrificed.)
- Line up your men in front of the door (shields & heavy weapons in front) and immediately open it.
- Kill as many aliens as you can on turn 1 as you can (you are on a time limit)
- After the first group is dead move your snipers up to the plant thing in the middle of the hallway while moving a shield carrier and a heavy weapon soldier to both doors on the left and right (you have to destroy both reactors and kill the high praetor all at once to finish the mission in time).
- Open the doors and kill the Andron guards (use the snipers in the center to finish off any that didn't die). Then move your shield and heavy weapons guys towards the second set of doors.
- In the next few turns use your snipers to push down the hallway and start assaulting the large open room at the end while your pairs of shield and heavy weapons guys fight the guards past the second set of doors.
- As soon as the reactor room guards are dead send a shield guy past the third set of doors on both sides and throw grenades onto the reactors. Have your heavy weapon guys run back to help the final push to the praetor.
- If you haven't already you need to send at least one guy forward into the large room so you can see the high praetor (he will be in the center of the doorway across the room). Once you can see him have all your snipers kill him. Have anyone still back in the reactor rooms start to run towards the high praetor and exit (the reapers will start to swarm soon if they haven't already).
- RUN! The reapers are closing in by now and you must fight through the few remaining aliens to get to the escape pods (the room behind the high praetor)