Blackfathom Depths Quests

Before Entering Instance:

Go to Ironforge and talk to Gerrig Bonegrip to start Knowledge in the Deeps

Go to Darnasus and talk to Argent Guard Manados to start Twilight Falls

Go to Darnasus and talk to Dawnwatcher Shaedlass to start In Search of Thaelrid (See “Inside the instance:”)

Go to Auberdine and talk to Argos Nightwhisper to start Researching the Corruption

Class Specific:

Warlocks go to The Barrens and talk to Doan Karhan to start The Orb of Soran'ruk

Horde only

Go to Stonetalon Mountains and talk to Tsunaman to start Trouble in the Deeps, which leads to The Essence of Aku'Mai quest in Ashenvale

Outside Entrance to Instance

Before entering Black fathom Deeps, kill Blackfathom Tide Priestess until they drop the Damp Note, which starts Allegiance to the Old Gods(Part 1), which leads to Allegiance to the Old Gods (Part 2)

Inside the instance:

Once in Blackfathom Deeps, talk to Argent Guard Thaelrid to start Blackfathom Villainy