Judging by Diablo's speech, they serve as a symbolic representation of the Nephalem's own fear, which they must defeat to escape the dark grasp of the Realm of Terror.
They mimic the appearance of the Nephalem heroes, although they are pitch dark in color (except for their equipped weapon), and are classified as Demons. Their damage and life do not scale with those of the character, but are immense compared to normal monsters, therefore each Shadow Clone is a formidable foe.
The Haunt of Vaxo also allows the summoning of Shadow Clones of the player, but these clones fight at the player's side for 15 seconds. They function in the same manner as Shadow Clones created by Diablo, except that their Life and damage do match those of the character.
In console version of the game, Nemesis may summon a Shadow Clone of each player it has slain.
In battle, Clones use the characters' own skills, not necessarily those currently equipped. Each clone has a fixed set of 1-3 abilities, randomly chosen in each game (meaning that in each battle, no matter how many Clones spawn and no matter the number of attempts, their skill set will remain same). Each ability will benefit from a predetermined skill rune.
Note: on some occasions, other skills or skill runes have been reported; however, Shapeshift skills, summoning of pets (with the exception of Hydra), healing and absorption skills are never used by Shadow Clones.
- Cleave (Gathering Storm), Hammer of the Ancients (Smash) and Leap (Call of Arreat)
- Bash (Pulverize), Ground Stomp (Wrenching Smash) and Furious Charge (Dreadnought)
- Weapon Throw (Ricochet), Hammer of the Ancients (Rolling Thunder) and Rend (Ravage)
- Frenzy (Vanguard) and Threatening Shout (Falter)
- Blessed Shield (Shattering Throw) and Shield Glare (Divine Verdict)
- Slash (Zeal), Sweep Attack (Gathering Sweep) and Condemn (Shattering Explosion)
- Slash (Carve) and Judgment (Resolved)
- Justice (Crack) and Blessed Hammer (Icebound Hammer)
- Hungering Arrow (Puncturing Arrow), Vault (Trail of Cinders) and Caltrops (Torturous Ground)
- Entangling Shot (Bounty Hunter), Multishot (Arsenal) and Marked for Death (Valley of Death)
- Evasive Fire (Displace) and Elemental Arrow (Screaming Skull)
- Grenade (Cluster Grenades) and Fan of Knives (Fan of Daggers)
- Fists of Thunder (Bounding Light), Mantra of Conviction (Overawe) and Sweeping Wind (Cyclone)
- Deadly Reach (Piercing Trident), Wave of Light (Wall of Light) and Cyclone Strike (Implosion)
- Crippling Wave (Tsunami), Exploding Palm (The Flesh is Weak) and Blinding Flash (Self Reflection)
- Way of the Hundred Fists (Windforce Flurry)
- Poison Dart (Splinters) and Locust Swarm (Pestilence)
- Poison Dart (Snake to the Face), Zombie Charger (Undeath) and Grasp of the Dead (Unbreakable Grasp)
- Plague of Toads (Rain of Toads) and Acid Cloud (Corpse Bomb)
- Spirit Barrage (Well of Souls) and Soul Harvest (Languish)