Major Mana Potion

Major Mana Potion is a potion that restores 1350 to 2250 mana.

Source
The alchemy recipe to create the Major Mana Potion is a rare (6%) drop from Darkmaster Gandling in Scholomance and can be purchased from Magnus Frostwake, a ghost in one of the buildings outside the entrance to Scholomance. Magnus is normally invisible, however; characters must complete the Scholomance quest chain "Justice for the Sarkhoffs," which begins with, to see him and purchase items from him.

It is crafted using by alchemists with a skill level of 295.