The Stormcaller is the new sub-class for the Warlock, and is a sub-class designed to offer high close quarter damage. As a Stormcaller Warlock you'll be able to utilise the powerful Stormtrance which allows you to fire lightning from your hands.
As you'll note below, the Stormcaller Warlock can improve their Grenades to gain area denial (Storm), or damage over time (Pulse). In addition, and as is standard with all Warlock sub-classes, their sub-class ability is known as Rift and allows them to improve themselves and their team. Finally and unlike other classes, the Warlock (and Voidwalker) gains access to Glide, allowing you to Blink.
Grenade
Pulse Grenade: A grenade that periodically damages enemies inside its explosive radius.
Storm Grenade: This grenade calls down a localized lightning storm.
Arcbolt Grenade: A grenade that chains bolts of lightning to nearby enemies.
Movement
Glide: Double jump in mid-air to activate Glide.
Modifiers
Focused Control: Upgrades Glide for better directional control while in mid-air.
Focused Burst: Upgrades Glide to provide an initial burst of speed.
Balanced Glide: Upgrades Glide to provide bonuses to both speed and control.
Super Ability
Stormtrance: Hold to fire Arc lightning from your hands.
Modifiers
Landfall: On casting Stormtrance, fire a bolt of lightning into the ground, creating a devastating shockwave under you.
Superconductor: Doubles your Stormtrance lightning's chaining capabilities.
Ionic Blink: Press L3 to teleport during Stormtrance.
Melee Ability
Thunderstrike: Deliver an electrocuting melee strike to close-range targets.
Modifiers
Chain Lightning: Your Thunderstrike chains from the struck target to another nearby enemy.
Amplitude: Your Thunderstrike has a greater range.
Rising Storm: Hits with Thunderstrike charge your Super Ability and Melee energy.
Class Modifiers
Arcane Wisdom: Training focused on battle recovery and speed.
Arcane Spirit: Training focused on battle recovery and toughness.
Arcane Force: Training focused on toughness and speed.
Ability Modifiers
Pulse Wave: When critically wounded, trigger a Pulsewave that boosts speed for you and your allies.
Feedback: Incoming melee attacks fully recharge and intensify your Thunderstrike.
Transcendence: When cast with full grenade and melee energy, Stormtrance restores your health to full and drains slower.
Attribute Modifiers
Ancestral Order: Training focused on all attributes.
Chaos Order: Training focused on raw speed.
Divine Order: Training focused on toughness at all costs.
Ability Modifiers
Electrostatic Mind: Stormtrance charges faster when allies are near. When Stormtrance is active, nearby enemies take damage.
Arc Web: Enemies damaged by your grenades chain deadly lightning to other nearby enemies.
Perpetual Charge: Getting a grenade kill recharges your melee. Getting a melee kill recharges your grenade.