The potion that Dumbledore drank is known as the Emerald Potion or the Drink of Despair. It is a mysterious potion that induces intense pain, fear, delirium, and extreme thirst. The potion was used to guard one of Voldemorts Horcruxes, Salazar Slytherins Locket, within The Cave. The potion could not be charmed, transfigured, scooped up, altered, or drained in any way, and it could only be drained away by drinking. Those who consumed the potion had to drink it all to escape its effects, but with at least three sips, the user would experience great internal pain, like burning. Then, they would feel immense fear and even relive some of their darkest memories. As an added icing on the cake, the potion would also create extreme thirst, which Voldemort used to his advantage as the water in the lake that surrounded the potion could be drunk but would give the Inferi a chance to pull the user into the depths. Dumbledore drank the potion to obtain the Horcrux and protect Harry from its effects.