SPOILERS FINALE
The finale takes place on Eden Prime,a perfect utopia built on the conspiracy theories of a Conrad. But it is a simulation. Questioning “truth” makes you vanish.The world is being run by two versions of the Rani:Mrs Flood and a second incarnation who is younger (bigeneration).They're doing an experiment to test whether belief in a fake, perfect reality can resurrect the dead.Omega is resurrected from the Underverse through the power of belief, and returns in a new form: a giant clawed hand with an eye in its palm. Alongside the Rani and Conrad, they become the “Unholy Trinity”: the Architect, the Herald, and the Vessel.Dr begins to see visions of Susan, and remembers the tree they planted on Gallifrey long ago. "the Tree of Forever" which they hoped would "reach other worlds"; roots extending into every simulation. Mel dies saving Ruby and Belinda from the Vlinx, who is a mole in UNIT used to hide Omega's presence. Dr uses the TARDIS to turn the Tree's roots into a reality bomb to collapse the illusion, returning free will to the people and weakening Omega, who feeds on belief. With his power gone, Omega is sealed into the roots of the Tree forever. The modern Rani betrays her younger self and attempts to escape, but is absorbed into the Underverse. Younger Rani is trapped in another simulation and locked in her own eternal cycle. Doctor is mortally wounded in the process by Omega's "gaze". Belinda chooses to stay behind to help rebuild Wish World into something real. Ruby returns to UNIT. Dr tells her she was more of a Doctor than he ever was.13 appears in a vision and tells him it’s okay to rest. 15: “We ran.We learned. We dared. And maybe, just maybe, we got it right. That’s all this ever was. A long, mad dash through the dark, holding hands with hope.” We never see who he becomes. postcredits, the TARDIS appears beside the tree. The doors open. cut to black. On screen: “The End”, then a slow fade-in: “?”