This quest is part of the Hero of the Mag'har quest chain.
Do not be alarmed by what you might see once the effect has taken hold! These spirits are all around us - always. The potion allows your mind to be able to understand and ultimately see the spirits. You will need to be under its influence if you are to speak with Mother Kashur.
You will find her a great ways to the southwest, at the Ancestral Grounds.
The potion that you drank has no real effect. You can only see a spirit if they allow it. The potion is merely a symbol of your belief and dedication. It was a test and you passed...