From WoWWiki

The Writhing Deep is the site of a silithid infestation in southeastern Feralas. It is a specific area for several quests in the zone.
Could also be considered to be Hive Zukk'ash, a minor silithid hive, considering the name of the silithid infesting the area.

Subzones of Feralas

Camp Mojache • Dire Maul • Dream Bough • Feathermoon Stronghold • Feral Scar Vale • The Forgotten Coast • Frayfeather Highlands • Gordunni Outpost • Grimtotem Compound • High Wilderness • Isle of Dread • Jademir Lake • Lariss Pavilion • Lower Wilds • Oneiros • Rage Scar Hold • Ruins of Isildien • Ruins of Ravenwind • Ruins of Solarsal • Sardor Isle • Shalzaru's Lair • Thalanaar • The Twin Colossals • Verdantis River • Wildwind Lake • Woodpaw Den • Woodpaw Hills • The Writhing Deep