Needless to say, spoilers ahead!

I just want to quickly outline off the top of my head the various endings available in the mod. The intention is not to have many endings just for their own sake, but rather to reflect what I believe are valid player choices. If you feel the story is reflecting your choices, then you feel ownership over it. That feeling of ownership sort of gives you "permission" to become emotionally invested in the outcomes, and that's really the golden goal I'm after -to make people *care*. In order to give a damn, you have to have true choices in front of you. 

So here we go, the list of endings:

Quest 1: There is no Umbra:

• 1: If, after reading his journal, you believe Ulves was right in trying to kill Daumbra before she has the chance to become Umbra again, then you can kill her right after you meet her, in the Sightless Pit. Of course, this requires you to have read the last page of his diary where he specifies the only way to truly kill her, namely, the "Daumbra Killer" blade, which you can obtain from the Atronach Forge if you follow his instructions. If you don't properly prepare to kill an unkillable Daedric Artifact, you will fail. But if you do, then that's the first possible ending.
• 2: In fact you can kill her any damn time using the "Daumbra Killer" blade! She'll sure be surprised.
  

• 3: When tempted by the Prince of Bargains, you may legitimately believe that Daumbra belongs with Clavicus, as she was made from him. Thus, you can surrender her to him, and he re-absorbs her. The end, and a victory for Law and Order I suppose.
• 4: You are also free to believe Clavicus is evil (although he has given you so far no reason to believe that, other than being the classical trickster god, Loki archetype) and giving Daumbra to him would increase his powers in ways he or the world don't deserve. If you also believe you have no other choice, then you can kill Daumbra yourself with the "Daumbra Killer" Ulves gives you. Ulves certainly makes a case for it. Sorry Daumbra, can't give Umbra the chance.
  

• 5: Soon after talking to Naenra you learn that you can erase her memories a second time around (the first one being Ulves' work, which is what originally turned Umbra into Daumbra). You can have a conversation with her about it... and it's interesting to wonder where the line is between asking someone to forget everything and asking someone to commit suicide. They're both pretty equivalent things depending on your concept of the afterlife. Still, if you arrive at the Atronach Forge, you learn that Ulves, the man who tried to kill her once (see number 1) and asked you to kill her again (see number 4) has "surprisingly" modified the Forge he created to... guess what? If you go along with him, she doesn't get her memories erased -she dies. Then you can have a chat with Ulves and learn his reasoning. At least he can now rest in peace.
  P.S. That's not the only outcome if you visit the Atronach Forge again. There is more content there, and you can avoid this bad ending with the right dialogue choices.
• 6: Wait, Naenra wants you to do what? To harvest bodies? Like Calixto did? Why madam, that's immoral. It's unethical, and I just won't have it. Thanks, but no thanks, and a good day to you! Tell Daumbra you want her to stay a sword, and tell Naenra you've decided to keep her as a sword, and she instantly gives up her plan and exits stage left (and as you will see next, she's not wrong). But Daumbra is secretly broken-hearted and will not treat you as warmly anymore from that point on. You've friendzoned her. Hey, at least she didn't die this time!
• 7: You can refuse to harvest bodies, but lie to Naenra about it. For a cunning witch who is hundreds of years old, she actually believes you, and lets you continue with the next stage of her plan! Tsk, tsk. This was incredibly hard to code because it required variations of every single dialogue after this point that would have normally referenced your harvesting activities. All the way up to Clavicus, and when you meet him again, you can agree to his bargain. I was surprised a lot of players actually went for it, for various very justifiable reasons. In this ending, Clavicus wins, but at least Daumbra doesn't die -and although she remains friendzoned, at least she's not as grumpy about it as with the previous one.
• 8: Of course, you can friendzone Daumbra and still reject Clavicus. This leads to perhaps the single worst ending in the entire story. Without any real "love" to rescue you from what Ulves saw coming miles away... you become Umbra permanently. "Told you so" he says, from the grave. Oops.
• 9: But let's say you did agree to harvest corpses. The Prince of Bargains finds your duplicity amusing. You get called out by the Trickster God. Does this make you more likely to agree with him? You certainly can. This is the second-best ending: Clavicus gets to stay, but Daumbra loves you and Umbra never returns. Probably good enough.
• 10. But the audience demands a grand finale! And dawn can only happen after the darkest of the night -which in this case is Umbra possessing you utterly. A scared Naenra thinks on her feet, wondering why didn't Daumbra's love win over Umbra, but quickly skedaddles before Umbra can eat her soul. And in Arcwind Point... Umbra can eat her soul. Similar to number 8 -this opens "The Umbra Run", and for the rest of your Skyrim experience you will not be able to use any other weapon. I'm sure someone will take it up as a challenge.
• 11. But let's say Naenra manages to yank the sword out of your hands and you beat Umbra temporarily with your combined efforts. Great. Now Naenra tells you that she knew Umbra would try to come back, but hoped Daumbra's love for you would win out. We're just going to try again with a little more oomph this time. Because you do love her, of course, right? Wait, you don't? Oh. Oh... you're already married? Uhh... I see. This is the "I never actually loved her" ending. Naenra takes her ball and leaves the playground. You should tell your actual wife and gain some points from this at least. 
• 12. No, you *do* love Daumbra! Go help her! This is her time of need -go be the light in her darkne-... aaand she's dead. Umbra won. You didn't reach her in time, you couldn't heal her. Umbra returns. Sure, you can beat Umbra again, but she'll come back eventually -she's a daedric artifact. And Daumbra is now gone. Sad stuff. 
• 13. Your light, which represents your love, heals her. Pretty interesting how Clavicus earlier mocked you for your seemingly impractical ideals, but now those ideals are what give Daumbra the strength to overcome Umbra. Even more interesting if for some reason you *didn't* earlier kill Daumbra's fears and insecurities inside her mind, represented by those ghostly little swords. You should have (which means "forgiving") because now you have to "love her" (light) "despite her flaws" (ghost swords) and really... if that doesn't mean true love then I don't know what does. And this is the happiest ending, in my view, and the canon one.
  

• Endings where she dies: 1, 2, 3, 4, 5, 8, 10, 11, 12
• Endings where she dies but leaves her corpse behind so you can wield her: 1, 2, 3, 4, 5
• Endings where Umbra wins: 8, 10, 11, 12
• Endings from which Chapter III can continue: 13