EVERYTHING about Sislo and Tetheril's marriage, and the boundless love they have for each other in spite of being practically different people. As you'll see throughout the story, it's hard not to see them as nothing less than couples goals.
This is all no accident, either. Word of God has stated time and time again that the story is essentially a tribute for the love he has for his own actual wife, who helped him with making it too.
Sislo and Tetheril helping a poor soul from being harassed and/or arrested by Druden men working for the Iron Industry.
While explaining his history with the Iron Industry to Tetheril, Sislo makes a point to tell her that she pulled him out of that past life.
Ovar turning out to be a friend of Tetheril's. He tried to rob her at one point, but then she gave him food instead of retaliating, and the rest is history.
After the fight with Zama, Sislo briefly lapses into despair at the knowledge that he has no hope of being blessed by his God before noticing Tetheril regaining consciousness. That alone makes him wonder if it's really all that hopeless after all.
Sislo refusing to kill Greiri even as she beats him into the ground demanding he does so. When the woman despairs at the pain of her suffering, Sislo lets her know that she's not the only one, and that she should try living in their memory instead of seeking out a worthy death.
When Gobby and Flint tell Sislo and Tetheril that the city they're going to, Syndstadt, is under the Iron Industry's thumb, Tetheril tearfully offers to call the search off so her husband doesn't have to go back to the ones who hurt him. Sislo simply states that so long as she's by his side, he doesn't mind at all.
While somewhat sad in that it ended with the dryad elder allowing himself to die, Tetheril's flashback to when she became proficient with healing magic. It ends with her being grateful that she grew into that path as she watches Sislo sleeping peacefully.
As Ovar predicted, Terethil manages to get through to Greiri and befriend her despite her incredibly rough exterior and brief outburst at the bar.
Sislo demanding that the succubus at the diner stop making advances on him. It's a Seduction-Proof Marriage, after all.
Tetheril tackling Sislo right as he was about to give in to ravenous fury thanks to Chela's words. His rage disappears immediately, and the two embrace. It is followed by a touching monologue by Sislo as he makes love to his wife. Unfortunately, it's capped off by him realizing that confronting Ondiox is the Point of No Return for him.
So it's been revealed that Sislo has been lying about his story of being a slave to Ondiox. The villain revealed the Awful Truth that he helped him form the current evil empire we know today out of graditude for freeing him from the last regime. What does Tetheril do? Leave him? Curse him? NO. She asks if she remembers his wedding vows to her. It stops him from following Ondiox, he recites them, and they embrace. THIS is the strength of true love.
Although it led to the foundation of the Iron Industry, there's something rather touching about how Ondiox freed Sislo when he was just a child. When you consider that he was under the boot heel of the previous regime too, you get the sense that maybe there was a time when the future Iron Lord was legitimately virtuous in his rebellion (before he got Drunk with Power, that is).
Sislo is fully prepared to not deserve Tetheril's love after all is revealed. His wife has this to say:
I can not say whether or not you deserve punishment. However, what I believe you deserve is a chance...You no longer wish to be that monster that they made. You hated that monster and so you wished to destroy it. You did not pretend to be a man, you wanted to be one. A good man. The man I love.
After that and Sislo deciding he must dismantle the empire he helped make, Tetheril offers to go with him, as do his friends (even if Gobby is being possessed by Chela). And when Tetheril sheepishly admits that they need more than one rose instead of just the one they got from Ondiox...she and Sislo burst out laughing. It's amazing how what was once the worst thing Sislo could imagine happening to their relationship ended up making it so much stronger.
Sislo and Tetheril enjoying themselves in a secluded lake before going to confront Ondiox.
Tetheril giving Sislo a Cooldown Hug to prevent him from fully succumbing to his bloodlust (which only spiked because he thought she was dead).
After defeating Chela spectacularly and seeing all the roses that grew in her wake, Tetheril puts off taking them so that she can protect Sislo.
Sislo and Tetheril embracing after the final fight is finally won. And for once, Sislo can tell her in earnest that he's okay.
As it turns out, most of the heists Ovar has gone on are for the sake of an orphanage he grew up in. And it's where he intends to send his share of Ondiox's fortune.
Greiri promising to protect her new Family of Choice (Sislo and pals) from this moment on.
After all that has happened, all the pain and revelations, Sislo, Tetheril, and all of their True Companions manage to earn their happy ending. They follow the cherufe into the new dawn, an Etrea now full of color without the Iron Industry to choke it out. And as Sislo and Tetheril walk towards it, hand in hand and ready to help others in need, we're treated to a montage of moments from their past. From when they first met, to their blossoming relationship, to the moment Sislo proposed to the love of his life, to finally their wedding. All to the tune of "Till We Meet Again".
