This is the trigger for the Burrower encounter in the Deep.
The event consists of 7 waves of spawns about 3 minutes apart.
Ancient Burrower Flesh Cap
Ancient Burrower Hide Tunic
Ancient Burrower Spine
Bile Drenched Flesh Robe
Brilliant Stone Ring
Ring of Living Ore
Ring of the Depths
Shard from Unfathomable Depths
Spell: Blessing of Aegolism
Spell: Cloak of the Akheva
Spell: Hammer of Souls
Spell: Khura's Focusing
Spell: Koadic's Endless Intellect
Spell: Mask of the Stalker
Spell: Moonfire
Spell: Speed of the Brood
Spell: Spirit of Khati Sha
Spell: Warder's Protection
Spell: Zevfeer's Theft of Vitae