"The Ancient One"

A "Non-Hostile" mob that is hidden in a far away structure (a temple of sorts) dressed in black and blue robes. Hard to find but rewards immeasurably. Once you find him you can interact with him for a quest to complete. (Quest should be geared towards mid to late game) on completion players can return to "The Ancient One" to recieve....."A Potion of Permenance" Once drank it will permanently buff your character. It could effect things like reach, a permanent level of efficiency effecting everything you hold, how long you hold your breath etc. This would create a unique late game challenge. This could also have potential for a good lore story. Thanks!