Upon the reopening of the Dark Portal to Outland, the Cenarion Circle dispatched an exploratory force, known as the Cenarion Expedition, to explore the uncharted world. Much like the Circle, it is a coalition of night elf and tauren forces. Since the opening of the Dark Portal, the Cenarion Expedition has quickly gained in size and autonomy, achieving enough power to be considered its own faction. The Expedition maintains its primary base at Cenarion Refuge in Zangarmarsh; it has also made its presence known on Hellfire Peninsula, in Terokkar Forest, and in the Blade's Edge Mountains. Cenarion Refuge is located immediately west of Thornfang Hill.

The Refuge is located in the Zangarmarsh for the primary reason of studying the rich wildlife located there. However, the Expedition has discovered troubling goings-on in the marsh. Water levels in many parts of Zangarmarsh are decreasing, and some areas such as the Dead Mire have already suffered greatly from this strange phenomenon. It has become known that this decrease in the water levels can be attributed to pumps that have been constructed in the Marsh by the naga. Their purpose is to create a new Well of Eternity for Illidan Stormrage. However, the Expedition cannot afford direct confrontation with the naga so numerous in the Zangarmarsh and Coilfang Reservoir. It needs the aid of those willing to assist the druids in their dangerous battle against those who seek to disturb the marsh's natural balance. Quite naturally, those heroic enough to fight the naga at Coilfang Reservoir will be well rewarded.

Reputation

Neutral to Honored
Kill Naga, while also running Coilfang: The Slave Pens whenever you can; a good instance run will net reputation faster than soloing. Alternatively, the player can begin turning in Unidentified Plant Parts for a chance at an Uncatalogued Species, which can be turned in for 500 reputation. It is suggested that the player save his Uncatalogued Species until after Honored status is achieved, as the quest cannot be continued past that point, while Uncatalogued Species can be used until Exalted.

If you are an herbalist, and interested in Sporeggar reputation, you may want to grind the Bog Lords which can be found in the NE, SE, and SW corners of Zangarmarsh. Their bodies can be "picked" by herbalists and often yield Unidentified Plant Parts, while every kill yields 15 reputation with Sporeggar.
Honored to Revered
Once the player is Honored, running Slave Pens and the Coilfang: The Underbog (with the exception of Hungarfen and some giants), will no longer grant reputation. You should now do any Cenarion Expedition quests in Hellfire Peninsula, Zangarmarsh, Terokkar Forest and the Blade's Edge Mountains. It is also the time to turn in any Uncatalogued Species you have found. Doing this should get you part of the way into Revered.

Alternatively, you can finish leveling to 70 and run Coilfang: The Steamvault. Each run gives just over 1500 reputation if you clear all mobs. Also within the Steamvault lies a repeatable quest, Orders from Lady Vashj, which begins with Orders from Lady Vashj. You will then be able to turn in Coilfang Armaments, which drop in both Steamvault and Slave Pens, receiving 250 reputation for the first turn-in and 75 reputation each thereafter. This turn-in is available all the way to Exalted.

Once you are 70 and have upgraded your gear, you can opt to run Slave Pens, Underbog, and Steamvault on Heroic Mode upon purchasing the Reservoir Key. While the instances are difficult, they award significant reputation: regular mobs are worth 15 reputation, 2 for non-elites, and 150/250 for bosses. This method works until Exalted.
Revered to Exalted
Continue with the same strategy as above: finish any remaining quests, run Steamvault, and continue with Coilfang Armaments turn-ins.

It is also possible to run Slave Pens, Underbog, and Steamvault on Heroic Mode. The reputation gained is not much more than running Steamvault in normal mode, whilst the time investment for heroic dungeons is much higher, possibly resulting in a lower net reputation per hour, however the loot is better and you will receive Badge of Justice from the bosses which can be used to purchase high quality epic gear.