My detailed discussion of Knights of the Fallen Empire's chapters approaches the end of the original story arc launched in October! Chapter eight is its grand finale. Needless to say, there will be spoilers.
You return to Asylum and Scorpio starts working on repairing the damage to the Gravestone in ways that Koth seems to have been unable to. Meanwhile, Lana has good news: "certain elements" from both the Republic and the Empire are interested in setting up an Alliance against the Eternal Throne.
You're interrupted by a holocall from Heskal, who wants you to come to the Scion hideout. T7 is happy to accompany you. You arrive to find dead Scions all over the floor... and witness Heskal getting killed by Arcann, who says that Heskal actually invited him to Asylum. He reveals that he killed the Scions because he considers himself to be above fate and offers you the option to surrender - all he asks is that you allow yourself to be re-frozen until he can figure out a way to get Valkorion out of your head and surrender the Gravestone.
Interestingly, you have the option to genuinely accept his offer, but when you call Lana she doesn't believe that you would really surrender and - get this - Valkorion actually appears to Arcann and tells him that he'll never be rid of him without killing you first. (Shoutout to xLetalis for showing this option on his channel - I'd never chosen it myself and was quite surprised by the outcome.) You also have the option to pretend to surrender and then warn your crew on the Gravestone. (Though that you do so right in front of Arcann seems a bit dumb - could have tried to get a bit further away first!) Finally, you can just attack him right away - you'll end up fighting either way. The ensuing fight is drawn-out and not very interesting except that you can use Arcann's own powers against him - if you get him to place his red circles on himself, he actually ends up stunning himself! Can't say that speaks for his competence...
Once you get Arcann to about half health, he knocks you back against a wall and we cut to an outside view of the Eternal Fleet arriving, as well as ships already fleeing from Asylum - a bit strange that they already know what's happening, especially if you didn't radio your crew. With upgraded targeting algorithms, the Gravestone shoots down an enemy ship that crashes right into the Scion hideout, causing Arcann to seemingly get buried under a giant collapsing pillar and giving you a chance to get away.
On the way out you have to fight skytroopers and knights, who as usual are everywhere instantly (sigh). You also find a couple of them dragging Heskal's body away, who has amazingly managed to not die yet despite of having received Arcann's lightsaber right through the chest. He confirms that he betrayed you because it was his fate and claims that the other Scions are still on your side, even though they will all die soon as part of a glorious future he has foreseen, before finally expiring for good (you can help with that if you like but he dies anyway).
We cut away to Arcann emerging from the rubble and instructing Vaylin, who's just landed troops on the ground, to spare no-one. On your way back to the Gravestone the background chatter that you heard from NPCs before has changed in amusing ways, with refugees who were previously moaning about their situation frantically looking for anywhere else to go. When you reach the ship, Lana tells you that the docking clamps have been locked down and you can't get away. Koth and HK are already on their way to the control spar to fix this, but they'll need help. Vaylin shows up and wants to kill you, but Senya interferes by Force-pushing you half a mile away (slightly strange way of being helpful) and says that this is a family matter. You and Lana leave her to face Vaylin alone and fight your way to the free zone to meet up with Koth. If you left Tanno Vik alive in chapter six, he's helping out with the fighting there as well.
Apparently HK-55 has already got ahead somehow, but you and Koth need to steal a shuttle to get up to the control spar while Lana stays behind to guard a chokepoint. Meanwhile Senya and Vaylin are duelling outside, with Senya vainly trying to reason with Vaylin to win her over to her cause. You meet up with HK, and he and Koth stay behind to defend against Zakuulan reinforcements while you take a cargo lift up to the actual control station.
The control room is strangely empty, though the kolto stations around its perimeter should be a warning that something bad is about to happen. Indeed, as soon as you go to use the console to release the Gravestone, Arcann appears out of nowhere and makes a lunge for you. HK-55 joins in to help you but the ensuing fight is still supremely annoying, as Arcann, like Revan, has a huge arsenal of knockdowns and stuns while being immune to them himself. There are power conduits around the room which you can smash to do some extra damage to him, but it can be tricky to get the smashing animation to complete as Arcann's attacks constantly interrupt it.
Once you finally get his health low enough, he suddenly knocks you down and HK has to throw himself into the line of fire to protect you, getting destroyed in the process. (Nooo...!) Arcann corners you, and Valkorion freezes time once more, urging you to use his powers to defend yourself. Interestingly, if you used Valkorion's powers on both previous occasions, you cannot refuse him - he will take over your body anyway. (Thanks to FibroJedi for this probably not widely known detail!) With Valkorion's power, you blast Arcann off the nearest rail... and hit some innocent refugee ships outside as well, as you're zapping just that hard. If you refuse Valkorion's help, Arcann actually stabs you in the stomach! However, either Koth or Lana show up just in time to dislodge a giant crate from the ceiling and use it to push Arcann off the nearest ledge anyway. Whether drained by Valkorion using you or because you took a lightsaber to the gut, you're not in a good state as you make your way back to the Gravestone.
Meanwhile, Senya has managed to best Vaylin in single combat but doesn't have the nerve to kill her. You and your crew make a successful escape, even though the Gravestone's special cannon isn't ready to inflict any damage. As your character collapses from pain on the bridge, Tora utters the unforgettable line: "Are you dying? Can I have your stuff?" As you pass out, we cut back to Arcann and Vaylin on Asylum. Arcann, who is of course completely unharmed after falling down a bottomless abyss, concludes that his father's power is weaker than it used to be, while Vaylin seems more determined than ever to kill their mother after she showed her mercy.
You wake up two days later, with everyone very concerned about you. You all update each other on what happened: Koth's crew suffered some losses and HK is supposed to be gone for good as his memory core couldn't be recovered. However, the good news is that the Republic and Imperial contacts that Lana mentioned at the beginning of the chapter have been convinced by the recent battle to throw their support behind you. You are to become the leader of a new Alliance based on the planet Odessen, which is where you are now headed.
Chapter eight is the grand conclusion to the first half of KotFE, and while I did some gentle chiding in my summary in terms of enemies and NPCs always miraculously being in the right (or wrong) place at the right time, it does its job well. It's hard not be emotionally affected by the Battle of Asylum: First there's Heskal betrayal (even if you didn't like him, it comes somewhat fast and suddenly), the big showdown between Senya and Vaylin, and finally the fight against Arcann, including HK's heroic sacrifice. (Though the emotional strength of that particular moment has been significantly
weakened after Bioware brought him back after all, plus there's the whole
flooding us with silly HK-themed items thing.)
I thought the final confrontation with Arcann was particularly well done - on my first playthrough I had been steadfast and always refused Valkorion's power, but when Arcann had me cornered I relented out of fear for my character's life - yes, even though I knew that practically, you're not going to die here no matter what, I was just that immersed.
In terms of NPC character development, Senya and Valkorion are probably the most interesting here. (Though you also get a chance for a bit of flirtation/romance with Lana and Koth). Senya's attempts to reason with Vaylin and failure to strike her down when she had the chance show that, despite of all her claims to the contrary, she isn't really ready to take that final step in the fight against her children. And Valkorion gets a chance to show his nastier side (if you make the right choices) that stands in contrast to his constant attempts at smooth-talking, by directly goading Arcann into attacking you if you offer to surrender and outright taking control of your body from you if you try to defy him and made the "wrong" choices before.
It feels like all the major pieces have been set up for a grand finale, but first it's time to catch our collective breath for a bit...