When using equipment with linked sockets, Support gems can be linked to Skill gems to augment the skills effect. You can link multiple support gems to a given skill to create interesting and powerful combinations. The following is a list of the announced support gems, and their effect on the skill they are combined with.

Added Chaos Damage
Adds chaos damage to a skill.

Added Cold Damage
Adds cold damage to a skill, giving it a chance to freeze targets.

Added Fire Damage
Adds fire damage to a skill, giving it a chance to ignite targets.

Added Lightning Damage
Adds lightning damage to a skill.

Burning Cold
Converts some of the skills cold damage to fire damage, and increases both cold and fire damage.

Chance to Ignite
Increases the skills chance to ignite enemies when dealing fire damage.

Concentrate Area of Effect
Reduces the radius of area of effect skills and increases their damage.

Faster Attacks
Increases the attack speed of physical skills.

Faster Casting
Increases the cast speed of magic skills.

Faster Projectiles
Increases the speed and damage of projectiles.

Increased Accuracy
Increases the skills accuracy.

Increased Area of Effect
Increases the radius of area of effect skills.

Increased Critical Damage
Increases the damage bonus from critical strikes.

Increased Critical Strikes
Increases the chance of causing a critical strike.

Increased Duration
Increases the duration of the skill.

Item Quantity
Increases the number of items dropped by monsters killed with this skill.

Item Rarity
Increases the rarity of items dropped by monsters killed with this skill.

Knockback
Causes damage from the skill to also knock enemies back.

Life Gain on Hit
Restores players life when they hit an enemy.

Life Leech
Restores players life based on damage dealt to enemies.

Mana Leech
Restores players mana based on damage dealt to enemies.

Melee Physical Damage
Increases melee physical damage dealt.

Minion Damage
Increases damage done by minions.

Minion Life
Increases minions life.

Minion Speed
Increases minions movement speed.

Multiple Projectiles
Causes additional projectiles to be fired by projectile skills.

Pierce
Gives projectile skills a chance to pierce their target and hit additional targets.

Reduced Mana Cost
Reduces the mana cost of the skill.

Stun
Increases the chance to stun enemies.

Weapon Elemental Damage
Increases elemental damage dealt by weapons.