House of Wolves is the second expansion for Destiny. It is scheduled to released on May 19, 2015. The main NPC for HoW will be Petra Venj, the Queen's Emissary previously found in Queen's Wrath event.
House of Wolves will introduce a variety of content including gear upgrade, 2 new social hubs, 1 new strike, 3 new story missions, 3 new quests, 1 new area/raid called The Prison of Elders, 1 new pvp mode called Trials of Osiris, 4 new pvp maps and a bunch of bounties.
New Features, Upgrades and Items
The new max Attack for legendary and exotic weapons is 365 (up from 300).
The new max Defense for legendary and exotic armor is ?? (up from ??).
All old Legendary and Exotic weapons and armor can be upgraded to the highest Attack (365) or highest light and defense with Ascend perk. Upgrading Legendary weapons and armor require Etheric Light and Exotic ones require Exotic Shard.
Reforge - re-roll the perks of HoW weapons at the gunsmith.
Material Exchange - Trade Ascendant Shard, Ascendant Energy, Mote of Light, Glimmer, Radiant Shard and Radiant Energy for each other at The Speaker.
Fallen Cores - obtained in Prison of Elders. Give to Variks for PoE weapons and armor.
NPCs
Petra Venj - main House of Wolves NPC, responsible for Queen's Wrath faction
Brother Vance - Trials of Osiris NPC
Variks, the Loyal - Prison of Elders and House of Judgement NPC
Social Spaces
Vestian Outpost - Main social space in The Reef, Asteroid Belt, similar to The Tower.
Halls of Amentet - 3 player social hub area in Mercury. Only players "tested" in Trials of Osiris can enter.
Strikes
The Shadow Thief - Level 28 Strike on the Moon
Story Missions
A Joining of Houses - Level 26 Story Mission in Old Russia, Earth.
An Army of Wolves - Level 26 Story Mission in Ishtar Sink, Venus.
The World Ravager - Level 28 Story Mission in Ishtar Sink, Venus.
Quests
Duel of the Silent Fang - Level 26 Quest in Old Russia, Earth.
Dark Raider - Level 28 Quest in Ocean of Storms, Moon.
Wolves' Gambit - Level 28 Quest in Ishtar Sink, Venus.
Arena / "Raid"
The Prison of Elders - 3 player, co-op Arena mode that replaces raids in previous Destiny editions. Located in The Reef, Asteroid Belt, The Prison of Elders requires the participants to be level 32+.
PvP Modes
Trials of Osiris - new competitive 3v3 PvP mode.
PvP Maps
Widow's Court - European Dead Zone, Earth
Thieves' Den - Ishtar Sink, Venus
The Timekeeper - Meridian Bay, Mars
Black Shield - Firebase Thuria, Phobos (Moon of Mars)