The Ancient Sentinel is at present, the hardest battle you will face in the game. So why put yourself through it? Well, there is a chance that it will drop one of its arms as a prize, known as the Melee and Ranged fragments (Again, clickable). These are arguably the two most powerful units in the game.
The below info should give you some help in defeating it. But be warned, you need various R6 units to do this effectively.
Everyone please feel free to add your own formation, tips, etc. You can even upload videos if you wish.
Apex Stalker MethodEdit
In this formation, a variation of the infantry method (see below), the Apex Stalker received from Boss Strike 4, the Infected Boss Strike, is placed in the front row, and uses his first attack (Cleave) on all three arms, often doing critical damage on the main body. Begin by freezing the ranged arm, and using the Cleave attack. Use a Mega Tank to finish off the Ranged Arm. If it is still alive after three turns, retreat and try again. Then focus all attacks on the main body, using the Radio Tech Precise Strike attack and Cleave whenever they are available. Mega Tanks can be swapped out for Legendary Boars or other high-damaging units.
Here is an example of an Apex Stalker formation using Trebuchets and a Collosus instead of Veterans: http://www.youtube.com/watch?v=qlNLe45SvLQ.
R6 Trebs MethodEdit
I (tab) have used this to kill it several times so far without nano healing, but it can be hard work. It does have the benefit of a lower healing bill, mainly lumber. Thanks to iisxxxxx for help with this. Scroll through the slideshow on the left for a walkthrough. You can probably replace the megas with high rank heaviers at a push. Totally ignore the arms, and start by firing raptors at the thing. If the main body fires his main beam, it will severely damage several of your trebs, and RT. So if this happens (and you will quickly learn what it looks like when he does), force quit the game. You have to be very quick. That's why you leave the arms, you want them to attack instead of the main body. Relaunch the game, click on the "red battle icon" to join the battle again, and try the same move. Often, it will then attack with an arm instead, and you can carry on. If the main body still attacks, try a couple more times, then try a different move instead. Sometimes firing with one of the mega tanks is what's needed to get it to change its move. If you can't stop the main body firing, you can probably continue if you have trebs left, and the RT has fired, but you will probably end up with just megas left near the end, and you will need to use nano healing when the megas are stunned. Once the armor is off, the trebs do much more damage. A couple of times, I have even managed to fire the RT twice, which means you lose hardly any units, but it took a long time, and a lot of quit and restarts.
PLEASE don't post this on the BN public forums. The force quit is probably something that will be fixed if it gets discussed too much, as it is something of a loophole. It has been put on there before, and everyone tried to shut him up quite quickly :-)
*Note: One of our members confirmed this method with R5 Hvyr tanks. That makes this the first method we have been able to identify without using nano units.
Brute Force MethodEdit
This is not the prettiest or most efficient method but it works and it got me by for a couple weeks until I developed better units. I don't recommend this method unless you are 100% set on defeating the AS and don't have other means. The one plus side to this method is that it only requires two units; R6 Megas (9) and an R4+ RT. It costs quite a few nanos to heal (10-20) and the placement of the Megas will effect number of nanos needed to complete. I usually only healed when all Megas were stunned or if I had less than 4 and one was below 100 HP. It is important to note that the AS will be very deceiving when this method is attempted because it will still have plenty of armor when it dies but obviously no HP. Also note that using a nano heal will skip your turn.
Freeze Ranged Arm MethodEdit
|This method is more efficient than the "Brute Force Method" because by disposing of the Ranged Arm you have a few turns that the AS cannot attack. Units required: R6 Megas, R4+ RT, R6 Treb or R6 TK, and a freezing unit of your choice. Yes, even the Cryo Trooper works with this setup but ET has more armor and draws an extra attack or two. As with all AS formations, placement of troops can be the difference between a win and a loss (See photo). Sequence of attack is also crucial in this method. My suggestion is as follows: Freeze Ranged Arm, Treb Raptor attack or TK Ranged Arm, Finish off Ranged Arm with Mega if need be (if TK is used more than one attack is necessary), Pound away at Main Body with Megas and use RT (Precise Attack) as soon as it is available. Loses will include: RT, Treb or TK, Freeze Unit and a few Megas. Nanos are usually needed but not always (depending on crits). Have at least 10 to be on the safe side, more if using Cryo and/or TK.|
This method uses high rank infantry in front row, rendering the melee arm fairly useless as its checker attack can only target tanks. R6 vets would be best, but other high defense/high dodge units at R6 will work, including Eagle Eyes and Raider Recruits. Freeze and kill ranged arm, with elemental troop or cyro trooper, and then an R6 treb or a tank killer. Then you need megas and an RT to work on the body. If the RT dies before it's first shot, or it's going badly, quit. High level blood ninjas do a lot of damage, but cost rare powder to heal. Use the Force Quit described in the R6 Trebs Method to improve your odds of surviving.