This is Sutekh’s world, and no one will be living in it. That’s what he wants.
So, how can the Doctor and UNIT stop him? Can they?
And what about Ruby? Will she finally know her parents?
Whatever the twist will be at the end, it better be a good one.
Actually, it is, followed by a couple of others

SPOILERS BELOW

The finale is actually provides doom and gloom thanks to Sutekh, but eventually hope that comes very slowly but arrives. It might even remind people of the final act of Avengers: Endgame.

Through most of the first half, Sutekh is supreme, dissolving all of creation into dust. Despite Melanie Bush’s (Bonnie Langford) bravado in the face of the Dust of Death Sutekh and Harriet release, al of creation dissolves. It even includes Cherry Sunday and Mrs. Flood (who dies by saying she had so many plans).

The Doctor and Mel eventually get to the Time Window with Ruby, who is still trying to identify her mom. Instead, she conjured a “remembered Tardis.” Before they get inside, Sutekh says he’s been hiding inside the TARDIS all this time, leaving his trail everywhere the Doctor has been. He was also able to conjure up Susan in all her forms this season. Thanks to that, all creation is dead. Even the Maestro would consider it too much gloom and doom.
At this point, the Doctor, Ruby and Mel are safely in the “TARDIS remembered”, which seems like an attic where bits and pieces of all his forms exits. Mel is glad to see Six’s coat and Seven’s sweater vest. Thanks to the screen from the Time Window, the Doctor sees some clips from “Pyramids of Mars”. He’s reminded why the other gods didn’t get rid of Sutekh.
They also pause to consider their position. All is dead except for them, and the Doctor thinks it’s all his fault. His cry of pain is a hard thing to hear.
So, all is lost?
For now, but Sutekh is going mad over Ruby’s secret, namely who is her mother and how come he never noticed her?
Is it because of the perception filter that keeps the TARDIS unnoticed from 73 yards away?

Cut to a desolate planet where there is a woman Sian Clifford) who has forgotten everything. People die, and so do memories. She thinks she has a daughter named Brindle. The Doctor, covered in a robe and hood, arrives to ask for….a spoon. The woman gives it to him before she dissolves.

How can a spoon save the universe? He attaches it to the TV screen, and it seems to give some answers on why Sutekh was there on Ruby Road. It also shows an unused clip from “73 Yards” where Roger ap Gwilliam (remember him?) explains how he wants to make a DNA registry for everyone in the UK in 2046. Ruby wonders why she remembers Roger, but the Doctor already knows him.
Anyway, they figure out if they head to 2046 they can find out who her mom is. Sutekh also learns how to possess the living, especially Mel. He figures he can learn about Ruby, too. She tries to fight it, though.
One they get closer to the truth, the snow returns, and freezes possessed Mel.

Finally, Sutekh uses the TARDIS to get everyone before him. He wants answers, and forces Ruby to reveal her mother’s name. She is reluctant to show him the screen….until she breaks it altogether. Sutekh is stunned he doesn’t notice she and the Doctor have got him on a leash of intelligent rope. He also finds out the TARDIS is well trained. A few whistles by the Doctor and Harriet (Genesis Lynea) is eliminated…and Mel is back to normal, too.

The TARDIS drags Sutekh though the Time Vortex, and crashes death against death to create life. Basically, the Doctor reverses what Sutekh did in a big way. It’s flashier than the last act of Endgame, but he gets the job done.
Oh, and that desolate planet from earlier? It’s full of life, and has a happy mom with a happy child named Brindle.
Susan Triad (Susan Twist) also gets a new lease on life. It turns out she was created when Sutekh was inspired by the memory of Susan Foreman. She later took many identities this season. Now, Miss Triad can be her own person
What about Sutekh? He’s back in the Time Vortex…until he dissolves.

So what about THE question about Ruby?
Well, her mom is a woman named Louise Miller (Faye McKeever), who had Ruby at 15. The dad was also 15. It was also discovered that the mom did use Ruby Road as her daughter’s name.
It’s just that simple, but makes sense to the Doctor. Sutekh thought Louise was important because others thought she was important. He knows that sometimes the most important people are the most ordinary, especially when they make important decisions. A lot of fans were hoping maybe Ruby’s the descendant of a Time Lord, or was a child in the wrong century. Instead, they made it a simple but important decision. By herself, Ruby is a great girl, no matter when she comes from.
It’s followed by a wonderful reunion, and the Doctor deciding Ruby should go. He does admit she changes his life because he never thought about his own family until she came around. That has to be a hint his granddaughter will be part of the show sometime. It can’t pass that up.

So it ends with a happy ending, except when Mrs. Flood (Anita Dobson) claims the Doctor’s story will end in absolute terror.

Does she think she’ll make that happen?
Either that, or she’s never seen how the Fourth Doctor’s story ends.
In any case, fans are upset her plans still haven’t been revealed or who she is. Maybe she is the next Big Bad.
UPDATE: Dobson said in the Radio Times Mrs. Flood will be back in 2025, and more will be revealed.
Here’s an idea: maybe she was a Time lady kicked out of Gallifrey unfairly and will take it out on the Doctor…but it won’t give her the satisfaction she wants. Something else will.

Anyway, it’s been an interesting series which introduced a memorable bad guy, a shocking return, a surprising love story, and comments about war and social media. Ncuti is making his mark as a memorable Doctor. It also doesn’t hurt that his constant costume changes will make cosplay much easier for fans.
Also, don’t think Millie Gibson is gone. Two other Companions made returns about taking breaks from the TARDIS, and Ruby will be the third. Also, she’ll be joined by another companion.
Aside from that…Who knows? At least he’ll be back for the holidays.