The Zombies are minor antagonists in The Power of Five horror series. They appear in Necropolis, the fourth book in the series.
Because the dark magic of the Old Ones can corrupt anyone it comes in contact with, either by giving dark sorcerers dark magic, or by mutating its practitioners (Diego Salamanda had an enlarged head) or by simply corrupting their personalities (Noah was insane) it is not surprising that when applied to the dead, the dark magic of the Old Ones can animate the dead or mutate them into being mindless corpses that serve only to command the Old Ones or whichever dark sorcerer commands them under the Old Ones at the time.
The zombies first appear in the fourth book, Necropolis.
During a time when the Gatekeepers Jamie, Scott, Pedro and Matt along with their guardians Richard and Professor Chambers get a midnight visit from a mysterious man named Ramon, from Lima, in Peru, Richard accidentally switches the security off, believing that Ramon is only staying a few hours or so and that he wasn't followed. Ramon hands over the Diary of Saint Joseph which describes the Old Ones in minute detail and he asks for protection in return. However, at that moment, Ramon is killed by a fence post thrown with superhuman strength from the darkness outside. Richard leaps to his feet and tries to turn on the outside lights but he cannot because dark magic is at work.
Matt realizes the Old Ones are here because it is freezing cold. Then he knows the creatures are here for the Diary as they shuffle into the light, and are revealed to be rotting corpses dressed in tattered clothes. They wield odd weapons such as chains and spikes and clubs. The zombies are impervious and unafraid of pain, they smash through windows with ease. When Ramon had been talking, more zombies had staggered upstairs and started a fire, later revealed to be in order to destroy Matt's passport. The real aim of the creatures is not to get the Diary back, but to ensure the Five get the Diary, and to destroy all hope of them getting to England to meet Scarlett.
The zombies appear in a huge variety of forms, all adult, and all in rotten clothing. One bizarrely wears a dinner suit. Matt can imagine them climbing out of a cemetery, suggesting their dark origins. The Five fight them off, using their respective powers. Jamie tells a zombie to impale himself and he does.
Matt also uses his powers to sweep up glass from the floor and it hits a zombie in the throat. When the zombies are killed they fall twitching to the ground, still alive, but not dying either. It seems only Incan weaponry can work against them, because when the zombies corner the Five outside the house and are about to maul them to death the Incas finally show up and shoot arrows at them. Maybe because the arrows are iron and iron is said to be a good defence against evil spirits. The Incas shoot arrows at the zombies and soon kill all of them.
But at a terrible cost: The zombies tear into Professor Chambers, wounding her badly, and she soon dies of blood loss.
In Hong Kong
When Scarlett is ambushed by the Old Ones in Hong Kong, the Triads get her to safety on the rooftop. More zombies chase her up to the roof and they corner her on the edge. Scarlett gives herself up for dead but Lohan shows her an invisible bridge in between the towers.
These zombies are like Yurei, which are Asian ghosts. The Yurei are typically dead white with black hair and ragged white robes. This is exactly how the zombies are described. It is said that the zombies in Hong Kong can appear human during the day and even at night. Matt apparently meets one of them staggering around the streets and he vomits everywhere. Many of the people in the crowds which Scarlett sees are either zombies or the Old Ones themselves.
All these zombies were apparently killed in the typhoon, or returned to Antarctica and were in the final battle.