Artery

Artery is one of Lord Loss' familiars. Some characters in the book also refer to him as the Hell Child. He appears in the books Lord Loss, Demon Thief, Slawter, and Demon Apocalypse. In Dark Calling, an Old Creature takes his appearance. Artery makes numerous key appearances throughout the series. In the book Lord Loss, he is one of the trio of Demonata that butchered Grubbs' parents. In Demon Thief Kernel kidnaps him and gives him a human appearance. He then convinces himself and others that this disguised demon is his brother, Art. He is finally killed in Demon Apocalypse by Bec.

Lord Loss
Artery, along with his sister Vein, is one of the trio of demons that kill Gret, Cal and Sharon Grady. Artery chases Grubbitch Grady down the stairs, and rips his jeans. Later in in the book, Grubbs battles Artery and Vein in an attempt to cure Bill-E of the lycanthropic disease. Dervish takes over the battle, and Grubbs challenges Lord Loss to chess.

Demon Thief
Artery plays a key role in Demon Thief. Kernel Fleck steals him and transforms him into a human child. When Kernel's parents go to an art fair, Artery (known as Art in his human form) is stolen by Cadaver. Kernel sees him at Lord Loss's Castle, and Artery enters the Board to taunt Kernel, Dervish and Shark. Artery is chased by Kernel, and is later revealed to be Art.

Slawter
Artery takes part in the battle when Lord Loss's familiars break through into Slawter. Artery faces Grubbs, and is considered an easy target when Grubbs needs to explode a demon to break the barrier.

Blood Beast
Artry appears near the end of the book, when he, Femur, Spine and Lord Loss kill everyone on an aeroplane.

When Juni Swan is magic, her eyes glow orange. This scares Grubbs, as he says that they look like Artery's eyes. Grubbs explains that when makes chanelchanel magic, they take it from the demon universe, and maybe we sometimes look a bit like them.

Demon Apocalypse
Artery appears at the beginning, when he is cornering Grubbs on a plane. Later, in the cave, Grubbs attacks him by swinging him into a stalagmite and throwing him into a wall. Artery is then killed by Bec MacConn.

Dark Calling
An Old Creature takes the form of Artery when he saves Kernel Fleck. The Old Creature also changes into Artery's form of Art, and Raz Wario.

Appearance
Artry takes the form of a small, green-skinned child with an oversized head. His eyes are balls of flame, and his head is always covered in small insects or pests, eating his skull. Sometimes they are lice, sometimes cockroaches or leeches. In his hands, are miniture mouths with sharp teach. He doesn't have a tongue in any of his mouths.

Vein
Vein is Artery's sister, and they fight Grubbs together. They seem to have a strong bond.

Lord Loss
Artery seems to be Lord Loss's favourite familiars, as he is seen serving the demon master on many occasions. Artery listens to Lord Loss, unlike Vein.

Cadaver
Cadaver is gentle to Artery when he steals him from Kernel Fleck, and rocks him gently and tickles him.

Kernel Fleck
When Artery is disguised as Art, he only obeys Kernel, and never bites him. He constantly bites other people, such as Melena and Caspian - his foster parents.

Trivia

 * Artery seems to be Lord Loss's favourite familiar.