It Rolls Downhill

How to do this quest properly:
First off, hunters and warlocks should dismiss their pets.
Second, make sure none of your AddOns removes the PetBar, as you will use it for this quest. Enable it!
Third, make sure you're wearing you Scourge Disguise at all times.

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• Use the teleporter to go outside, and find yourself a Blight Geist.
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• Use the Scepter of Suggestion you have in your backpack to make the Geist follow you around as your pet.
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• Go to the nearest Crystallized Blight (yellow crystals).
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• Use the first (and only) skill on your Pet Bar. It will make the Geist go to a crystal, take it and walk up to the Voltarus teleporter. Make sure you can actually see the Geist walk up to the teleporter and disappear, this is what gives you credit for the quest.
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I had a problem where my geist would dissapear randomly shortly after charming (not enough time to gather a crystal), i solved this by removing my ghoul disguise (right-click the buff) and putting it back on, worked like a charm.

An action bar is supposed to pop up I think. If it doesn't, you'll have to press CTRL + 1 to command them to get the crystals.