In a large pitcher, combine the fresh lemon juice and granulated sugar. Stir well until the sugar is completely dissolved.
Add the water to the pitcher and mix until fully combined. If using activated charcoal, add it now and stir until evenly distributed.
In a blender, puree the blueberries and blackberries until smooth. Strain the mixture through a fine mesh sieve to remove seeds, if desired.
Pour the berry puree into the lemonade mixture and stir well to combine.
Chill the Witches’ Brew Lemonade in the refrigerator for at least 1 hour before serving.
Serve over ice cubes in glasses, and garnish with lemon slices and mint leaves.