Lost in Action
In The Underbog, only part of this task is fulfilled.

Learn about the fates of Earthbinder Rayge, Naturalist Bite, Weeder Greenthumb, and Windcaller Claw. Then, in Zangarmarsh, return to Watcher Jhang at Coilfang Reservoir.

The Underbog is home to Earthbinder Rayge and Windcaller Claw.
Earthbinder Rayge may be discovered in the hall after defeating Ghaz’an Windcaller Claw as a bear previously dubbed “Claw” in a cage with the third boss, Swamplord Musel’ek. First, defeat the boss, including Claw, till they talk to you.
The Slave Pens are home to Naturalist Bite and Weeder Greenthumb.

Minimum Level: 62
Starts/Ends: Watcher Jhang (outside instances), Coilfang Reservoir (within instances), /way 52.2 36.0 Reward: 500 Cenarion Expedition reputation 22,000 experience

The Underbog Sporeggar Faction Quests

Bring Me A Shrubbery!
Collect 5 Sanguine Hibiscus and return them to Gzhun’tt in Zangarmarsh at Sporeggar. In The Underbog, Sanguine Hibiscus are dropped by shamblers, bog giants, and underbats.

Once completed, Bring Me Another Shrubbery! becomes a repeatable task. This may be done all the way up to Exalted and gives the same reputation as the original task but no additional experience.
Minimum Quest Level: 63 NPC
Begin/End Points: Gzhun’tt, Sporeggar, Zangarmarsh, /way 19.6 50.2 Reward: 250 Sporeggar reputation 22,000 experience

Oh, It’s On!
Return an Underspore Frond to T’shu at Sporeggar in Zangarmarsh.

This may be discovered inside The Underspore, a gigantic spiky plant just before the first bridge, behind the first boss, Hungarfen.
63 is the minimum level.
NPC quest
T’shu, Sporeggar, Zangarmarsh, and /way are the places where the story begins and ends. /way 19.4 49.6
22,000 experience, 350 reputation with Sporeggar

Stalk the Stalker
Bring the Black Stalker’s Brain to Khn’nix at Sporeggar in Zangarmarsh.

This kills the fourth boss, The Black Stalker.
Minimum Quest Level: 63 NPC
Begin/End Points: Khn’nix, Sporeggar, Zangarmarsh, /way 19,6 49,6
22,000 experience, 350 reputation with Sporeggar