The hallways that the Torment chases Valkyrie and Skulduggery through in Playing With Fire are the same kind that provides an escape hatch in the Faceless Ones!
In the first book, Skulduggery says he could be a figment of his own imagination. Later on in the series, he points out that Valkyrie could be Darquesse's good mood. In Death Bringer, he is revealed to be Lord Vile in the same way Valkyrie is Darquesse.
When Tanith walked into his house, Fergus was gaping like an idiot. He has met/seen China, so what says he hasn't met/seen Tanith? Possibly years before the twins were born and Tanith still looks young as she was.
I've just realised what makes Lord Vile such a ridiculously powerful Necromancer. He's a dead thing using death magic! Which, as we see in Mortal Coil, is not good news.
I just noticed that Death Bringer, the book title, could refer to Melancholia, Valkyrie or Lord Vile! Since all three of them show up in the climax, and all three are candidates for the mantle of Death Bringer.
Somewhere in between Fridge Heartwarming and Fridge Tearjerker, but Anton Shudder's "I prefer hugs" comment in "Last Stand of Dead Men" makes a lot more sense if you think about Larrikin's failed attempt to hug him in the backstory.
On the other hand, there is something terrifying in the fact that a mere Muggle came so close to killing a powerful witch. Imagine somebody without Reflection and Darquesse at her disposal.
Remnant!Tanith has access to Kenspeckle Grouse's memories. She knows how to build Desolation Engines.
In Kingdom of the Wicked, Kitana and her cronies were all in full view when Skulduggery turned into Vile and Val turned into Darquesse for the end fight. If the three of them knew the significance of Vile and Darquesse, they could identify them for a more well-informed mage.
More like Fridge Squick, but in the first book Stephanie keeps her underwear on the floor! That's decidedly unhygienic!
Fletcher can teleport anywhere he's been. He demonstrates the ability to teleport into the ocean at the end of Book 4. So why the hell didn't he just teleport Dusk there and turn the fight into a Curb-Stomp Battle?
Maybe because Dusk is so freaking awesome he'd kill Fletcher in the second it took them to teleport?
The thing is that in the fight Fletcher DOES teleport him. They just return with Fletcher unconscious and Dusk none the worse for wear. It still stands to reason that Fletcher could have killed him by taking him to the ocean.
Also, remember that we're talking about the third book, pre-Level In Badass. When he got scared, he teleported at the most 12 feet away, to the bathroom, and this was just after he opened the gate to the Faceless One's world, so he's bound to be tired on top of terrified.
To clarify, the scene referred to is the fight at the football stadium in book four. To reiterate - he teleports somewhere undescribed and gets his ass handed to him, and yet mere minutes later he teleports the bombout in the ocean. The fact remains that the series would be lacking a recurring villain rather quickly if Fletcher had remembered he could do that a little sooner.
Maybe Fletcher didn't know salt water kills vampires. Or he just can't always think on his feet.
Wait a moment, didn't they end up teleporting back after their fight? How the hell did they manage that if Fletcher was unconscious, I'd like to know?
Maybe Dusk knocked him out partway through the teleportation. Or forced Fletcher to bring them back and then knocked him out.
Also, If Valkyrie's coat is impenetrable, how was the fabric cut to make the coat?
Her coat isn't impenetrable. It's magically enhanced, yeah, but not made out of metal or anything.
Why do all the necromancers use such impractical things as their focus objects? They're powerless without them, and yet Valkyrie's the only one with enough sense to use something small, portable and inconspicuous. It's outright stated that the necromancers in the airport failed so badly because their focus objects were all in their luggage.
It's implied that the object you place your magic in influences the way you can fight with it. Take Viles armor for example. It's not only a powerful weapon, but also an almost inpenetratable defense. Another necromancer used a flintlock pistol and shot shadow bullets with it. Using a small object might make for better concealment, but wouldn't be suited to the persons fighting style.
Returning to a previous point, why actually a ring, that can be easily misplaced or snatched? Why not, say, a collar or a steel bracelett? Why not an item that is implanted into the body?
How comes it is still so hard for Valkyrie to use her Elemental Powers? In Book 6, she is attacked by Moore and cannot use it! At some point she even has time to rummage through her clothes for the necromancer ring, but still cannot concentrate enought for a fireball!
I'm pretty sure it's mentioned somewhere that Elemental magic does take at least a lifetime to become competent in, and in the first book Skulduggery says that most sorcerers choose Adept magic because "it's more immediately powerful." Skulduggery had absolutely nothing else to do except practise magic (well, and be tortured) when he was in the Faceless Ones' dimension and it still took him about a year to learn how to fly.
Necromancy also has been noted to come very easy to Val, and she likes to fight the quick and dirty way, using the easiest methods at her disposal.
What would happen if the reflection got, say, a haircut and Valkyrie didn't? In all of the illustrations, Val's hair is identical, but it would have grown at some point, and her parents must have said at some point "OK, Steph, you're hair's way too long. You need a haircut. But then Valkyrie would come home from fireball practice and they'd have thought, OK, your hair's growing suspiciously quickly..."