Forsaken Thicket Waters
“Before completion: The waters in Forsaken Thicket are known to have cleansing properties that can cure various afflictions. Those who possess this Mastery can wash away their ailments and afflictions when the opportunity presents itself.
After completion: You can now bathe in the healing Forsaken Thicket waters and cleanse your afflictions.
— In-game description
Forsaken Thicket Waters negates the damage from using the cleansing fountains during the encounter against Matthias Gabrel to cleanse Corruption, and allows use of the Thicket Waters during the Siege the Stronghold encounter.
If the player does not have Forsaken Thicket Waters mastery, using a Cleansing fountain during the fight against Matthias Gabrel deals heavy damage and stuns for 3 seconds.