Demons (The Last Trials)

"Demons, consider them as proto-devils, do you remember when everyone told you to not open the Gap ? Well, below Underworld is Hell and it's a dangerous place, it's where Demons live"

- Death to Rias Gremory The Demons are the very first inhabitants of Hell, and by extension, of Underworld, they were created by Great Red to test creation but The Darkness managed to corrupt them.

They live in Hell, a place below even Underworld, the Demons are served by Infernals.

The Demons are separated in two categories : the Prime Evils who are the three first creations of Great Red and the Lesser Evils who are the four last creations of Great Red.

To walk in our world or even in Underworld, the Prime Evils need to have a vessel, each created a Gear which corrupted its wearer.

Prime Evils

 * Mephistopheles: The First Demon, Lord of Hatred
 * Baal: The Second Demon, Lord of Destruction
 * Diablo: The Third Demon, Lord of Terror

Lesser Evils

 * Belial: The Fourth Demon, Lord of Deception
 * Andariel : The Fourth Demon, Maiden of Anguish
 * Duriel: The Fourth Demon, Lord of Pain
 * Azmodan: The Fourth Demon, Lord of Sin

Vessels

 * Sankekur: High-Priest of the Church of Light, Serve as Mephistopheles' Vessel
 * Tal Rasha: Leader of the Horadrims, a group founded by Raphael to fight the Demons, Serve as Baal's Vessel
 * Aidan: Prince of Tristram, Serve as Diablo's Vessel

Unholy Weapons
The seven Unholy Weapons were seven "Sacred" Gears created by the Demons to corrupt humanity, probably due to a lack of imagination, all Demons gave their true names to the Gears If molten, the seven Unholy Weapons can be mixed to form Tat'ametos, a Longinus and the only one strong enough to greatly harm The Darkness
 * Dul'Mephistos: Mephistopheles' Hatred Spear
 * Tor'Baalos: Baal's Destruction Claw
 * Al'Diabolos: Diablo's Terror Sword
 * Rim'Belialos: Belial's Deception Axe
 * Pan'darielos: Andariel's Anguish Scepter
 * Buc'durielos: Duriel's Pain Dagger
 * Maz'modanos: Azmodan's Sin Hammer