Permanent Potion of Longevity (5e Equipment)
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When you drink this potion, your physical age is reduced by 1D10+7 years, to a minimum of 17 years (If you are younger than 17, your physical age is increased to ~17 years old instead). Immediately afterwards, you gain the Boon of Immortality.
This potion in particular should be extremely sought after, but completely mysterious to even the highest level alchemists and mages. An entire campaign could be built around the level of quest that surrounds the acquiring of this potion, which should be more arduous than perhaps anything else in the campaign.