Diablo/Abilities and Gear

Abilities
High hand-to-hand combat skills, can clad himself in Demon Lord's Ambition (Haki) and was able to beat Shion and Beretta in hand-to-hand combat.

After Evolving into a Demon God, his EP becomes approximately 4,000,000~5,000,000+.

Magic

 * Dark Magic
 * Magic Energy Manipulation Archive
 * High Demon Summoning

Species Skill

 * Temptation

Ultimate Skill

 * Temptation King Azazel
 * Thought acceleration
 * Space Time Control
 * Multidimensional Barrier
 * All of creation
 * Penalty Domination
 * Temptation world

Unique Skills

 * Great Wiseman: (disappeared after gaining Ultimate Skill Temptation King Azazel)
 * Thought Acceleration
 * Thought Domination
 * Incantation Void


 * Enchanter: (evolved into Ultimate Skill Temptation King Azazel)
 * Fascination
 * Seduction

Extra Skills

 * Multiple Barrier
 * Spatial Travel

Daily Skills

 * Universal Perception
 * Demon Lord's Haki

Battle Skills

 * Phenomenon Control
 * Charm Domination
 * Torus Secret Art

Resistances

 * Physical Attack Immunity
 * Abnormal Status Immunity
 * Mental Attack Immunity
 * Natural Elements Immunity
 * Hybrid Attack Resistance

Equipment

 * Scissors (Bladed Claw Scissors): The appearance is like three claws and symmetric. The length of each claw being 1 m, a sharp double-edged sword. A special weapon made by Kurobee for Diablo (it was destroyed by Benimaru).

Chronological Breakdown
It seems Diablo was a member of a faction of demons called the Progenitors (Primordials). They were the royals of demon kind.