Death

Death a.k.a. The Shadow, as it is referred to by The Disciples, is the leader of all Demonata. It is the natural force of Death with a conciousness, making it extremely deadly.

Demon Apocalypse
Lord Loss and Nadia Moore served Death to achieve his goal.

Death's Shadow
The Shadow's identiy was revealed in the end of the chapter. It also brought back the dead in the form of zombies.

Wolf Island (book)
Grubbs, Beranabus, and Kernel have been torturing other demons about the identiy of The Shadow.

Dark Calling
Raz Warlo (Old Creatures) reveals to Kernel. Death was created when Bec cheated death in Bec (book). It worked in secrecy for hundreds of years, before revealing itself to numerous demon masters, including Lord Loss. It overpowered them and became the leader of all Demonata. Because of its power, it promised all demons that they would have eternal life.

Hell's Heroes
Death's physical form is destroyed in Hell's Heroes when the Kah-Gash turns back time to recreate a safer Universe.

In the same book, Grubbs, Bec and Kernel recreate the universe, except in the restarted universe, Bec never cheated death, and therefore Death never developed a consciousness.

Appearances
The Shadow looks like a giant octopus, with many tentacles. There are mouth's on the tentacles. It has very good grip, as Bec couldn't escape from it without assistance. It looks like it is made with patches of darkness, which are souls of the dead which have been brought back. The soul of Beranabus was part of the Shadow until its body was destroyed for the first time.

Personality
It hates all living things.

Power and Abilities
The Shadow is Death, so it has a variety of powers and abilities.

One unique ability is the power to resurrect the dead. It resurrected Nadia Moore and thousands of people on the ship where it fought Beranabus.

The body is not composed of solid matter so Shadow can be cut apart. However, it can also heal itself from all wounds, as revealed when Beranabus stabbed it.

Death's tenteacles have the capability to penetrate, as shown in Death's Shadow, where it killed Beranabus. When Bec was in the Shadow's grip, she felt excruciating pain as the Shadow tried to extract the piece of Kah-Gash from her.

Weakness
Although the Shadow is a unique creature, it had one weakness which was exploited in Dark Calling. A window could be opened directly into the Shadow, and the physical body can be temporarily destroyed from the inside. Opening a window into Death is not easy, even for Kernel. When Death realised living beings were inside him, he unleashed tendrils much like the ones outside of his body.