Stamina is a game mechanic that controls how many activities you can do before needing to rest. It's represented by a green bar at the top of the HUD below your Vitality. Stamina Recovery is an important part of balancing your combat and gameplay.
Stamina consumption is determined by the moveset of the Trick Weapon, and affected by certain Blood Gems. Sprinting, evasive actions, and blocking with the Wooden Shield also consume stamina. Evading consumes 10 per dodge, and sprinting consumes a relative amount per second..
It has been discovered that Vitality hides an Equipment Load hidden stat, that determines your stamina recovery rate when using armor. Details on this mechanic are not yet fully known.