WoW Legendary Item: Shadowmourne Unveiled and Quest Video

Just like Atiesh, Greatstaff of the Guardian for Naxxramas and Thori'dal, the Stars' Fury for Sunwell, a new legendary item will appeare in Icecrown Citadel, along with an epic quest chain.

Shadowmourne Spell Details

• Item - Shadowmourne Legendary - Your weapon swings have a chance to drain a Soul Fragment from their victims. When you have acquired 10 Soul Fragments you will unleash the Souls of the Damned, dealing 6840 to 7560 shadow damage split between all enemies within 8 yards.
• Soul Fragment - Gained a Soul Fragment. When 10 Soul Fragments are accumulated, they will release, triggering the Souls of the Damned.
• Souls of the Damned - Deals 6840 to 7560 Shadow damage, split between all enemies within 8 yards of the impact crater.

Quote from MMO-Champion

About Shadowmourne Legendary Axe

A two-handed axe that will drop in Icecrown Citadel (presumably from the Lich King himself) instead of Frostmourne.

Shadowmourne

This is a chain of quest that seems only available in the 25-Player version of the raid instance. It appears to award Shadowmourne, the legendary two-handed axe Blizzard showed on Blizzcon. The quests indicate that earning the axe is going to be a long and perilous journey, that only the most powerful of heroes will be able to undertake.