- Audience-Alienating Premise: The books feature anthropomorphic rodents... pitted against Gods of Evil and their bloodthirsty minions. Violent deaths abound, including decapitation and flaying alive in ritual sacrifice. The cute animal characters would put off older kids, but the stories are Nightmare Fuel for the younger ones. This is likely why these books have yet to see a film adaptation. What age group could it be marketed to?
- Complete Monster:
- Jupiter is a powerful sorcerer and the Big Bad for the original trilogy. Born as a deformed kitten named Leech, he grew envious of his older brother and hated him for possessing magical powers he longed to have. After he lets his brother die in a fire, he gains control of his body and later becomes a malicious god-like entity. With hundreds of rats at his disposal, Jupiter forced his army to dig underground so he could unleash the Plague onto the world, and allowed his rats to slaughter dozens of innocents. When his plans to unleash the Plague fail and his spirit is trapped in limbo, he cajoles Madame Akkikuyu to try and resurrect him, and even convinces her to bring a corn dolly to life, which later went on and murdered two Fennywolder mouselets. Once his spirit was released, Jupiter quickly took control of a power station and started to freeze the city. After gaining more power, he brainwashes Morgan into bringing his horde of rats to the station so he can kill them all and use their spirits as his new soldiers. He then attacks Audrey Brown's friends and family, killing several of them all while he attempts to destroy the sun and start a new ice age. A savage, bloodthirsty cat who demanded to be worshipped by all, Jupiter only cared about killing his brother and destroying the world, no matter how many innocent lives were lost or how many loved ones he chose to neglect.
- Deptford Histories:
- Lady Morwenna, from The Oaken Throne, is the traitorous handmaiden for the Starwife and the High Priestess for the Hobbers. After years of planning, Morwenna betrays and kills the Starwife before ordering Rohgar and his legion of bats to destroy Greenreach; anyone who survived was fed to her pet toads. Seeking the Silver Acorn, Morwenna also has the bats bomb Ysabelle's hometown of Coll Regalis, before ordering the Hobbers to hunt her and her friends down and kill anyone who gets in their way. After the Hobbers and bats fail, Morwenna finds Ysabelle herself while posing as a good Samaritan, and later steals the Acorn from her and tries to feed her to her toads. With the Acorn in her possession, she wastes no time betraying and killing Rohgar, and once Hobb is resurrected, she immediately tries to use him to kill Ysabelle. A cunning squirrel who enjoyed hearing her victims scream, Morwenna stands out as being one of the few villains in the series who resurrected a demon and nearly used him to Take Over the World.
- Wendel Maculatum, also from The Oaken Throne, is a traitor in disguise and the High Priest for the Hobbers. Posing as a comical jester, he traveled alongside Ysabelle and her group in hopes of acquiring the Silver Acorn. After separating from her group, he and his Hobbers kidnap or kill her and her friends before he uses the Acorn and the blood of three dead squirrels to summon Hobb. He and his Hobbers constantly stalk and taunt Ysabelle's group as they travel through the woods, even going as far as throwing a mouse's head at them just to scare them. When his true identity is discovered by Tysle Symkin, the former immediately murders the latter and flays his corpse, leaving it for Ysabelle's friends to find. His Hobbers later attack and destroy a stronghold full of warriors; while fleeing with Ysabelle's group, he finally reveals his identity and gloats how Ysabelle and her friends are doomed, and nonchalantly taunts Giraldus over Tysle's death. Even after Wendel dies, he reappears as a ghost just to kill Vesper out of spite and to fulfill a curse he placed on him earlier.
- Thomas: The unnamed High Priest of Sarpedon is the leader of the Scale, which longs to resurrect the serpent god Sarpedon, also known as Suruth Scarophion and Gorscarrigern. Seeking nine fragments of a jade egg, the high priest and his vast Scale army scourged the world and killed anyone in their path. After running into the Calliope, he capsizes the ship and kills hundreds onboard before heading to the Temple of the Twelve Maidens and massacring everyone in and around the temple, leaving their defiled corpses to be found later. After acquiring the seventh fragment, the high priest and his army head to Hara, where he attacks the city and slaughters thousands in hopes of finding another fragment. Once the high priest steals the last two fragments from Thomas, Woodget, and Simoon, he takes them all to the Black Temple so he can resurrect Sarpedon and offer them to the god as a sacrifice. When Thomas and his friends greatly damage the high priest's army, he chases after Thomas's crew using a statue possessed by Sarpedon's spirit, longing to kill them out of spite.
- Jerkass Woobie: Isaac Nettle. You can't help but feel sorry for him as he grieves over the death of his son, even though he was abusive towards him. It was heartbreaking when he found the owl pellet containing Jenkin's mousebrass.
- Uncanny Valley: The illustrations, to some extent, but considering the book's content this is likely intentional.
- What Do You Mean, It's for Kids?: While these books feature cute animals, many of them are subjected to violent, absolutely horrific deaths such as being skinned alive, decapitated, or having their body slowly eaten away by a deadly poison.
- The Woobie: There are plenty of these, with Audrey and Ysabelle being among the most notable examples.
YMMV / Deptford Mice