This chest spawns following the raid event "The Return of King Xorbb" (see this quest entry for details).
Arwyn's Greatbow of Valor
Brutal Frostbite of the Valley Master
Charred Spaulders
Draining Ire of the Glen Liege
Dread Armguards
Dread Boots
Dread Bracer
Dread Gloves
Dread Helm
Dread Leggings
Dread Tunic
Elfield's Belt of Many Pouches
Glowing Terrormote
Greater Terrormote
King's Vengeful Scowl
Lesser Terrormote
Primed Fragment of Fearlinked Zeal
Shardspike Adorned Cloak
Star of Xorbb
Vale Lord's Crystal
Vale Lord's Sieging Eye
Xorbb's Insight
Xorbb's Resolution of Vengeance
Xorbb's Rod of Retribution