- Moral Event Horizon: The Master gets a proper new body again, he destroys one-quarter of the universe, including the home planet of one of the Doctor's companions (though admittedly that was an accident he caused by going on a killing spree). And the new body he got is the corpse of said companion's father. After that, there was really no going back for that incarnation.
- Special Effects Failure: During the wonderful Tear Jerker finale, while the Doctor is staggering about on the rickety bridge trying to save the universe with both he and the audience knowing he's going to die, he is being watched for unclear reasons by what is obviously a cardboard cutout of Anthony Ainley.
- Visual Effects of Awesome: The regeneration, particularly the cocoon effect.
- What Do You Mean, It's Not Symbolic?: Programmers who use code to hold the universe together are portrayed as chanting monks in a monastery, the Doctor is followed by an apparition who seems like both a revenant and a guardian angel. There is a distinctly Tarotic vibe with a Tower, a Hanged Man, a Judgement and arguably a King of Wands. The constellation Cassiopeia, named for a monarch turned upside down for vanity, is significant in the climax in which the Doctor dies and is resurrected in an inverted and diminished form. There are whole books dedicated to puzzling out what the symbolism in this one means, such as El Sandifer's Recursive Occlusion (an explicitly occultist reading).
YMMV / Doctor Who S18 E7 "Logopolis"