Archon

Archon is a Mastery Arcane spell used by s in Diablo III.

Lore
The Archon is a being of pure Arcane energy. The Wizard Vyr claimed that it existed on another plane of reality, and constructed the Black Obelisk to try and gather its power. . Fearing he would bring doom upon them all, his acolytes murdered him, and the obelisk was destroyed.

Currently, the technique is able to be used by another Wizard.

In-game
Archon transforms the player, replacing all normal skills with Archon abilities. Every enemy killed while in Archon form increases all damage done by 6% for the remaining duration, stacking infinitely, making the Wizard near-invincible in combat with numerous lesser foes. This damage buff is multiplicative to other similar modifiers, but the stacks themselves are added up rather than multiplied.

All Archon abilities cost no Arcane Power to cast. While in this form, the player is also immune to all forms of Crowd Control, existing effects are removed.

The ability is very effective against numerous monsters (due to damage buff stacking rapidly) and against Illusionist elite monsters (since destroyed illusions count as kills). Familiar, Magic Weapon and Armor spells remain active when Archon is activated, but cannot be renewed until the Archon fades. Because Archon attacks cost no Arcane Power and must be used in a limited amount of time, they benefit greatly from Increased Attack Speed.

Archon Abilities
All Archon abilities ignore line of sight, obstacles and Waller affix barricades, but cannot pierce through solid walls. Unless a rune with different damage type is selected, they use Arcane damage type. Vyr's Amazing Arcana set picks the damage type that currently has the highest elemental skill damage bonus. Arcane Strike (Default LMB): melee skill, slams the ground in front of Archon, blasting all enemies within a roughly 10 yards radius circle for 790% damage. Only hits the area in front of the Archon, has no effect on enemies behind the Wizard: the circle is placed so that its outer edge barely touches the Wizard. Disintegration Wave (Default RMB): uninterrupted beam that pierces through enemies in shape of a reversed cone (broad side is large enough to damage enemies directly to the left and right of the Archon) for 779% damage per tick. Killed enemies are disintegrated, leaving no corpse. The beam is roughly 50-55 yards long (a little bit longer than the graphics show). Arcane Blast (Default 1): releases an energy blast hitting enemies around the Archon within roughly 20 yards for 604% damage. Has no cooldown (technically, 0.5 seconds). Does NOT interrupt the Disintegration Wave and Arcane Strike, and can be cast while moving.

Runes:

 * Combustion: Upon activation of Archon, the Wizard releases a blast that hits enemies within yards of him/her for  damage as Fire. The damage type of all abilities changes to Fire.
 * Teleport: Archon form adds one more ability (default 2): Teleport with cooldown reduced to seconds. This Teleport does not benefit from enhancements of a regular, but will gain Wormhole rune from Cosmic Strand or removed cooldown from Aether Walker. 
 * Pure Power:  Archon's cooldown is reduced by seconds (to  seconds). The damage type of all abilities changes to Lightning as well.
 * Slow Time: Archon form adds one more ability (default 2): Slow Time with no cooldown, placed atop of Archon and following them as they move. Using the ability again drops the shield. In addition, the damage type of all abilities changes to Cold, Arcane Strike and Arcane Blast will Freeze affected enemies for 1 second. This Slow Time will benefit from most enhancements of a regular Slow Time, and can even gain all runes from Crown of the Primus.
 * Improved Archon: All damage dealt by Archon abilities is increased by, stacking multiplicatively with the damage buff for killing enemies and general skill damage increases.

Non-rune enhancements:

 * Fazula's Improbable Chain (Legendary Belt): activating Archon form immediately adds 40-50 kill stacks.
 * Halcyon's Ascent (Legendary Amulet): Upon casting Archon, makes nearby enemies jump uncontrollably for 6-8 seconds.
 * The Swami (Legendary Wizard Hat): all bonuses from Archon kill stacks remain for additional 15–20 seconds after Archon expires.
 * Vyr's Amazing Arcana Set (Set Bonus for 2 items): Archon gains the effects of all runes at once. Elemental Damage type is chosen by the highest elemental skill bonus the player has.
 * Vyr's Amazing Arcana Set (Set Bonus for 4 items): each Archon kill stack also increases Attack Speed, all Resistances and Armor by 1%.
 * Vyr's Amazing Arcana Set (Set Bonus for 6 items): each hit or tick of damage of Archon abilities also adds an Archon kill stack. Archon stacks also reduce damage taken by 0.15% and have their damage bonus increased to 100% each.
 * Chantodo's Resolve Set (Set Bonus for 2 items): for every spell cast outside Archon form that hits an enemy, Wizard generates a charge of Wave of Destruction, stacking up to 20 times. While in Archon form, deals 4000% damage per second to all enemies within 30 yards, increased by 4000% per stack.
 * Crown of the Primus (Legendary Wizard Hat): grants all skill runes to Slow Time.
 * Aether Walker (Legendary Wand): removes the cooldown of Teleport.
 * Cosmic Strand (Legendary Source): adds Wormhole rune to Teleport.
 * Delsere's Magnum Opus Set (Set Bonus for 4 items): while Slow Time sphere is active, the Wizard takes 60% reduced damage, and their allies take 30% reduced damage as long as within a Slow Time sphere.

Development
In the later days of 1.0, Archon lasted only 15 seconds, but also gained 1 second in the total duration for each enemy that the Wizard killed (or at least had damaged before someone else killed that enemy) while in the Archon form. This, to a certain extent, was like the perma-Wrath Barbarian, in that as long as the form was allowed to persist, the Wizard was practically unstoppable, and dealt staggering amounts of damage. It is for this reason that it was rebalanced in 2.0, being given the damage increase per kill.

In patch 1.0.3., a bug allowed the Wizard to become permanently invulnerable by combining Archon and Teleport (Fracture) spells. This bug existed for months, and was only fixed when someone reported it on the official forum.

Prior to patch 2.0.5., all Archon runes were doing Arcane damage.

Prior to patch 2.1, Archon was the only shapeshifting skill that did not grant the Crowd Control immunity.

Trivia

 * The last tier of armor in Diablo III (before the Reaper of Souls) is named Archon.
 * Archons of similar design exist in StarCraft, being powerful protoss units.
 * This is the Wizard's transformation skill which boosts powers and changes appearance, each class (barring the Witch Doctor) has one and all of them give the added bonus of immunity to Crowd Control (post patch 2.1 only for Archon however as noted above); the other class equivalents are: Vengeance (Demon Hunter), Akarat's Champion (Crusader), Epiphany (Monk), Land of the Dead (Necromancer) and Wrath of the Berserker (Barbarian).
 * Archon is the only Shapeshift skill (the only other may be Angry Chicken) that always replaces the normal skills with special, shape-specific abilities, and as such, the only one that interrupts casting.
 * While normally the Wizard floats in air above ground in Archon form, they will still use their normal standing animation for Town Portal cast.