Units with this rule may gain one of two different sets of effects depending on whether they show up Sober or Drunk on the Battlefield.
Sober:
The Drunkard unit is miraculously sober for once. Sober models gain Vanguard and Light Troops. A unit that has been Sober once loses Scoring for the rest of the game.
Drunk:
The Drunkard unit is unbelievably drunk. Drunk models gain Immune to Psychology and Thunderous Charge. Drunk units cannot Ambush.
The player must choose before the battle whether a Drunkard unit is Sober or Drunk. Drunk Characters cannot join units containing any Sober models, and vice-versa (models without Drunkard are considered neither Drunk or Sober).