The Tavern is unlocked by purchasing it in the Tier 2 Town Hall upgrades.
You may purchase drinks you have found in dungeons to gain special buffs to aid you on your journey.
Once you rescue the Thief from the Prison, you will be allowed gamble.
Gambling is a simple card flipping game where the highest card number wins.
A draw will result in the 'house' winning.
The 'Spike Trap' card is the Joker, and will win any hand.
Richard is unlocked with the Tavern by default, and will allow you to purchase drinks that you have found in barrels throughout the Tower.