Kingsmead
The recipe for Kingsmead has existed in European occult circles for at least two thousand years, with significant gaps. The brew can only be made from honey from a beehive on Crown lands (however you define ‘Crown’): when properly prepared, it gives the drinker the ability to shrug off pain and wounds (half all damage taken, and damage regenerates in one-third the usual time) taken while in the Crown’s service. Traditionally, it was given to only the most loyal royal bodyguards and household troops, and those who took it kept it secret.