Rampage: You don't fucking get it, do you? Glory: We're her friends, Lacunae: That means... P-21 She doesn't have to fight alone!
Following the destruction of Stable 99, Blackjack - teetering on the edge of the Despair Event Horizon - inadvertently gets in contact with DJ Pon3/Homage, who makes a point of showing BJ all the good she's done.
Shortly afterwards, Spike's last-second intervention, preventing Blackjack from killing herself. He goes on to restore her will to live by showing her the Gardens of Equestria.
After a bloody and tragic battle, Lacunae stops to cremate the corpses. Notably, she explains herself by criticising her own Hive Mind.
Blackjack: What are you doing? Lacunae: What a Goddess should.
Chapter 34. All of it. Especially the moments between Blackjack and Littlepip.
P-21 finally admitting, both to Scotch and himself, that he's her father. He sings to her, with Blackjack, Glory, Lacunae, and even Rampage joining in. And at the end, Scotch starts to cry under her bandages, and he wipes the tear away, causing her to whimper "Daddy..." before they hug one another.
Despite her anger with Blackjack, Glory takes the time to make sure that she is feeling better, physically and emotionally, before she kicks her ass for cheating on her.
In Chapter 51, Scotch Tape gets her cutie mark. P-21 immediately comes over and gives her a hug.
Shortly afterwards, Glory is reunited with her mother, Dawn.
In Chapter 62, Blackjack's otherwise horrific "upgrading" session in Lighthooves' cyberpony device has one small bright point: it reveals that she's pregnant!
In the same chapter, Boo finally starts talking. Her first word? "Bwackjack."
Chapter 74 is a massive Tear Jerker, but it has one moment that stands out as this. Namely, Blackjack meets the real Luna's soul, the two comparing their mistakes and how they caused so many lives to be lost. Luna then asks how they could make up for it all, and what they should do now. Blackjack simply touches horns with Luna, and they recite the oath Blackjack took together.
“We do everything we can to make up for it, knowing that we’ll never succeed in getting rid of the guilt. We devote ourselves to spending every second trying to do better despite the fact that it will never be enough. And we pray with every single good act we do that somehow, when our lives are over, that our lifetimes will come close to making up for the wrong we committed.”
In the final moments of chapter 77, with the Eater destroyed and the souls released, Blackjack smells her mother's mane, hears P-21 chuckle, and feels a grey (likely Glory's) wing caress her cheek just before Luna's soul leaves her body, and she stares into the sky, smiling as her technology runs out of energy, and she dies looking at the souls that she set free.
In the finale set centuries later, Blackjack, having been resurrected years after Horizons, is shown to be living as a companion to Littlepip as both are effectively immortal. And at the very end, Blackjack and Littlepip journey to the moon, where they find Rampage's body, her talisman exhausted. Blackjack however, manages to activate it one final time, resurrecting her and destroying it in the process which releases all the souls within. The story ends with this:
“So, where are we going?” Rampage asked, actually sounding like a filly for the first time ever.
I hugged her close and reached over to put a hoof across Littlepip’s shoulders as she guided us back to Equus. “Home,” I answered her. “We’re going home.”