From Destinypedia, the Destiny wiki
- "A spark can give life...or take it."
- — Grimoire.
Arc is one of several known manifestations of the Light, along with Solar and Void. It is also one the classes of elemental damage.
- "Arc energy's not just electricity. Lot more finicky than that. Fission."
- — Banshee-44
Arc Light is related to electricity and electromagnetism, and can be wielded by Guardians to generate lightning bolts and other electromagnetic phenomena. Many of the Golden Age technologies of Humanity possesses circuitry, generators that run on Arc Energy, including weapons as well as tech that produces holograms. Vex are known to have a hindrance to exposure to Arc Energy, although this would be if they weren't attempting to harness it.  Arc is even found in the weather system itself. Arc energy can be found in Dark Ether with how the Screebs and Abominations use their attacks. Concentrated Arc can even distort space, and enough of it can even hinder Transmat usage. 
According to Osiris, Arc is the element of motion and conduction, and is created when the electromagnetic forces of our universe struggle to achieve balance. According to Ikora, Arc teaches that change is a fundamental aspect of the universe, and that "to wield it is to ride the storm of the unguessable".
Guardian subclasses that channel Arc energy use it to increase speed and close combat power.
Striker Titans use arc light to charge their fists with lightning to obliterate their foes with a deadly close-range ability known as Fist of Havoc. In Destiny 2 they can also gather Arc Light to transform into a missile in a super known as Thundercrash to deal massive impact damage.
Bladedancer Hunters use arc light to manifest a pair of daggers known as Arc Blades.
Arcstrider Hunters replaced Bladedancers in Destiny 2 and use arc light to create a fighting staff known as an Arc Staff. They can also throw this Arc Staff to create a damaging field known as Gathering Storm.
Stormcaller Warlocks use Arc Light to destroy their enemies with the power of the storm known as Stormtrance. By concentrating the Arc Light into a smaller area, they can unleash a long-range, more accurate beam known as Chaos Reach.
Common effects of Arc subclasses, as defined in the Light 3.0 update, are:
- Amplified - Your movement speed and weapon handling are greatly increased. After sprinting for a short time, you enter Speed Booster, further increasing your sprint speed and granting damage resistance against PvE combatants.
- By default, rapidly defeating multiple targets with Arc damage will amplify you. Your equipped Aspects and Fragments provide additional methods to become and benefit from being amplified.
- Ionic Trace - A bolt of pure Arc energy that travels along the ground, seeking its creator. When picked up, Ionic Traces grant Grenade, Melee, and Class Ability energy.
- Blind - Combatants are disoriented and cannot fire their weapons. Enemy players' HUD is removed and their vision is obscured. Strong against Unstoppable Champions.
- Jolted - The target is energized with destructive Arc Light. As they take additional damage while jolted, they chain lightning to nearby enemies. This chain lightning can occur multiple times while a target is jolted. Strong against Overload Champions.
As of the Arc 3.0 update, all grenades are accessible to all classes.
- Skip Grenade: A grenade which splits on impact, creating multiple projectiles which seek targets.
- Flux Grenade: An explosive grenade that attaches to targets.
- Arcbolt Grenade: A grenade that chains bolts of lightning to nearby targets.
- Pulse Grenade: A grenade that periodically damages targets within its explosion radius.
- Storm Grenade: A grenade that calls down a focused lightning storm.
- Flashbang Grenade: An explosive grenade that damages and blinds nearby targets.
- Lightning Grenade: A grenade that sticks to any surface and emits bolts of lightning.
Shared effects that can be exchanged to customize the powers of a subclass.
- Spark of Amplitude: Rapidly defeating targets while you are amplified creates an Orb of Power.
- Spark of Beacons: While you are amplified, your Arc Special weapon final blows create a blinding explosion.
- Spark of Brilliance: Defeating a blinded target with precision damage creates a blinding explosion. +10 Intellect.
- Spark of Discharge: Arc weapon final blows have a chance to create an Ionic Trace. -10 Strength.
- Spark of Feedback: Taking melee damage briefly increases your outgoing melee damage. +10 Resilience.
- Spark of Focus: After sprinting for a short duration, your class ability regeneration is increased. -10 Mobility.
- Spark of Frequency: Melee hits greatly increase your reload speed for a short duration.
- Spark of Ions: Defeating a jolted target creates an Ionic Trace.
- Spark of Magnitude: Your lingering Arc grenades (Lightning Grenade, Pulse Grenade, and Storm Grenade) have extended duration.
- Spark of Momentum: Sliding over ammo bricks reloads your equipped weapon and grants a small amount of melee energy.
- Spark of Recharge: While critically wounded, your melee and grenade energy regenerate more quickly.
- Spark of Resistance: While surrounded by combatants, you are more resistant to incoming damage. +10 Strength.
- Spark of Shock: Your grenades jolt targets. -10 Discipline.
- Spark of Volts: Finishers make you amplified. +10 Recovery.
- Spark of Instinct: When critically wounded, taking damage from nearby targets emits a burst of damaging Arc energy that jolts targets.
- Spark of Hope: You have greatly increased mobility, resilience, and recovery while sprinting.
The Fallen are the main users of Arc weapons, with all their light, medium and melee weapons, as well as many Abilities, sporting this damage type. The Taken and Hive also use Arc damage across many of their weapons, most famously the Hive Boomer. The Scorn reserve Arc damage for the rare Scorn Mine Launchers and the attacks of Abominations. In Destiny, the Cabal had no Arc weapons, with Psion melees and shockwaves being the only source of the damage, but in Destiny 2 they started issuing the Cabal Slug Shotgun in large amounts to Legionaries and Phalanxes, though Psions switched to Void abilities. Common Vex don't use Arc weapons, but the explosions of Fanatics, as well as the pools of Radiolaria commonly encountered in their territory deal Arc damage.
Arc Absorption Shields are used by Fallen Captains, Taken Centurions, Scorn Chieftains and Blood Guard Legionaries, and are added to Colossi, Knights and Harpies in higher difficulty activities, such as Legend Nightfalls.
- Worldline Zero
- The Wardcliff Coil
- Patience and Time
- Hard Light
- Heir Apparent
- Legend of Acrius
- The Fourth Horseman
- The Queenbreaker
- Trinity Ghoul
- The Prospector
- Dreg's Promise
- Zhalo Supercell
- Plan C
- Dead Messenger
- Grand Overture
List of appearances