The team realizes that Bo protected them with the horseshoe forged by the gods. It's a pretty big risk to take and Bo is weathering it the best she can. Back at Hades' groovy apartment, she slips Tamsin a key to the cell with a kiss, and pretends to kill her. But Hades is onto this plan – he shouts at her, wears her down, and then watches as Bo (omgsies! THIS!) sucks the chi out of everyone in the city!
The gang realizes what's happening as they drive through town in Vex's impressive van. Their worst fears are realized, Bo has gone full Pyrapus and killed just about everyone except for them: everyone including the dark and the light Fae in The Dal. Bo proclaims herself the Queen over all the Fae, and that's when Hades realizes that there are still some people alive and sends her off to find her old friends.
Hades gets all of the cops of the city to become his servants, but the horseshoe is still protecting the gang – that is until Tamsin arrives in full Valkyrie mode and takes down the cops. It's a brief safety, because soon Bo arrives in full evil Queen mode and the only one who can bring her back is her heart: Kenzi, who tells her all kinds of adorable rhyming things. Unfortunately, it doesn't work and Bo breaks the horseshoe and steals all of their chi!
That's when the flashbacks start. Bo remembers the love of her family and stops herself just in time – this is when Bo realizes that the only way she can take down Hades is to go full Pyrapus: even though it's a risk that she'll kill everyone again. That's when Tamsin goes into labor. The most powerful Fae arrive – under Hades control - and Hades returns to confront Bo. Epic battles ensue! Vex tries to mesmer the Fae, Lauren delivers Tamsin's baby, Bo and Hades engage in a battle with their hands and her power overcomes his. Why? Because she has both light and dark inside her while he just has darkness. Let that be a lesson to us all.
After defeating Hades, Bo goes full powerful Queen and gives everyone their chi back from the rooftop of Vex's van just as the team gathers to meet Tamsin's baby and Vex and Marc bond and end up holding hands. When Bo wants to breathe chi into Tamsin (because remember that all Valkyries die in childbirth), Tamsin refuses, names the baby Dagny, and dies. Or as it's called for Valkyries in their last life: rising.
Bo leaves the baby in the care of Kenzi and goes off to save the world, gets pretty much engaged to Lauren, and then everyone goes flashing forward to the future, where a teenage Dagny is taken to the Dal. Dagny signs the ledger, is told she doesn't have to choose between light and dark anymore and learns evil is coming for her, as is evidenced by the handprint Hades left on her (remember, her dad is Hades). When she asks what happens next, Bo tells her they'll protect her. And so they will…