- Complete Monster:
- Susan Mortlake is one of the Chief Executives of Nightrise, and is Colton Banes and Kyle Hovey's direct superior. When they and report back to Susan Mortlake that Jamie escaped them, she concludes that one of them has to die and has Colton strangle Kyle. She then takes Scott Tyler to a Hellhole Prison where she and Colton torture him into helping them assassinate a Senator, analyzing his cries of pain like a symphony. She has him mind control the senator's bodyguard into killing him, so that the death will not be linked back to Nightrise.
- Colton Banes is an assassin for Nightrise hired to track down Jamie and Scott, two of "The Five". When Jamie escapes Colton kills "Uncle Don", the stage manager they were staying, and his wife to pin the rap on Jamie. When he and his partner Kyle Hovey report back to Susan Mortlake, she has Colton strangle Kyle. Colton does this immediately and without remorse, stating the he always hated Kyle. When Jamie tries to scan him to find Scott's location, he sees, in addition to Colton's other crimes, memories of a girl locked in a battered trailer with puncture wounds. When Jamie tries to go to prison under an alias, he is caught and one the guards reports him to Colton. Colton tells the guard to turn off the air conditioning in the cell, which the guard does reluctantly. During the raid on the prison Colton shoots Jamie in the back.
- Oblivion: The new chairman of Nightrise is introduced by holding a press conference with ten thousand members of Nightrise, and says that they will be taken away to have their limbs cut off and replaced with weapons for the battle with the five. When one member refuses, the chairman has him shot dead before sending guards in to beat everyone up and take them away by force. The chairman orders his second-in-command, Jonas Mortlake (Susans son), to make Scott do a FaceHeel Turn so that without him, the five will never be united, telling Jonas that if he fails, he will suffer the same fate as the other members of Nightrise. When Matt and Richard are captured, the chairman has Matt crucified and tortured by having his skin flayed and his bones broken. The chairman tries to kill Richard in front of Matt, stating that Matt will be Forced to Watch his best friend die, and will than continue to be tortured forever.
- Ensemble Darkhorse: Richard Cole and Lohan - the latter because he's a badass Triad assassin who nevertheless is heroic and honorable, and the former because he's the exact opposite - but no less badass. Even Horowitz has admitted that they're his favorite characters.
- Everyone Is Jesus in Purgatory: Matt's story is suspiciously similar to the life of Jesus. Born with special powers according to some higher plan, destined to save the world from The Legions of Hell and their very Satan-like leader, leads a small group of followers of whom the closest to him is named Pedro ('Peter' in Spanish), accepts his destiny despite wishing there was another way, betrayed by one of his companions, flogged and beaten and hung up to be jeered at, died, came back and ascended to Heaven right in front of his friends.
- Iron Woobie: Matt, once he learns that his destiny is to be tortured by the Old Ones and given a Mercy Kill by Richard and still manages to keep going.
- Jerkass Woobie: Scott, especially after the abuse he goes through at the hands of Susan Mortlake.
- Nightmare Fuel: By the bucketloads. The violent deaths of most of the villains are only the least of it. Listing all the scary things in Necropolis and Oblivion would basically just be a recap page.
- Stoic Woobie: Matt again, by the last book. Also Pedro, who never really complains despite being a starving street urchin who spends most of his pagetime being hunted, abused, betrayed, nearly killed on several occasions and repeatedly exhausting himself trying to use his power on grievously-injured people who often don't make it anyway.
- They Wasted a Perfectly Good Character: Of the twelve leaders of the Nexus, most of them pretty interesting characters, only two of them both of whom die. appear in Oblivion while a third suffered from a case of Dropped a Bridge on Him during the Time Skip. Making this even worse is that while one of those two is Big Good Susan Ashwood, the other is a literal Ascended Extra who was present at the meetings but never spoke or was specifically described during the previous books. The most blatant example of this trope is the unnamed Bishop, who could easily have appeared during the scenes set at the Vatican and either provided some minor aid to Pedro or provided a case of Dramatic Irony by being unaware of his presence. This is somewhat mitigated by the implication that the other leaders of the Nexus are out there, rallying support for the World Army, but Horowitz still could have done more with them.
- Uncanny Valley: Shape changers pretending to be humans have this effect. Of the few that are mentioned, not a single one has maintained their deception for any length of time: One lets his disguise slip when he meets Scarlett, the other has a freakishly round head, one can't speak, one doesn't notice cutting his own thumb off, and one doesn't notice an enormous insect crawling over his eye. The best impersonation so far has been "Audrey Cheng", and even it gave the game away when it forgot to eat. Scarlett rumbled it when she realized the only time she had ever seen "her" express hunger was looking at a fishmonger's slab.
- What Do You Mean, It's Not Political?: The Old Ones vote Republican. No, really.
- Horowitz never says which party is which, only that the guy under the control of the Old Ones (Baker) is the nominee of one of the major parties and Trelawney is the other's. It could be interpreted either way: the environmental and social justice stuff make the Old Ones sound Republican, while from a religious perspective they're more likely to be backing the Democrat. However, several hints do favor this interpretation, most notably that the anti-Old-One candidate, thinking the security he's surrounded by, notes that only one crazy person with a gun is enough to make it necessary, that it is very easy to get a gun, and he might want to change this. That's a much more likely set of thoughts for a Democrat than a Republican.
- What Do You Mean, It's for Kids?: The books are fairly scary and deal with some fairly adult themes.
YMMV / The Power of Five