Health Capacity, or Maximum Hit Points (HP), is the amount of damage a character can take before they die. Health is displayed at the top left of the HUD as spheres filled with red. One full bubble of health represents 2 hit points, and a bubblr partially filled in represents a single hit point. Bosses' health is also displayed in the HUD on the right side at all times. Other Enemies also have health, but it is never displayed to the player.
Shovel Knight starts with 8 Health at the start of Shovel of Hope. Health Capacity can be increased by 2 points by buying meals from the Gastronomer in exchange for Meal Tickets. 3 Meal Tickets can be purchased from the Goatician (for the prices of 1000, 4000, and 6000 respectively) with 3 more being found in the chest at Shovel Knight's camp each time he clears a quadrant of The Valley, for a maximum of 20 Hit points after redeeming all of the Meal Tickets in the game.
Like Shovel Knight, Plague Knight starts with 8 health points as well. Unlike Shovel Knight, there are no Meal Tickets for Plague Knight to redeem. Instead, after completing each quadrant of The Valley, Mona (Or Percy) will give Plague Knight a Health Potion, increasing his health capacity by 2 points each time, for a maximum of 14 permanent Hit Points. His health can be further upgraded (albeit temporarily) through the use of Health Tonics, which increase his health capacity by 2 points for each tonic consumed until he dies. These can be used to give Plague Knight a Temporary maximum Health Capacity of 20, but no more.
In Specter of Torment, Specter Knight is not alive and therefore does not have Health, but instead has Will, which contributes to his Will Capacity, or Maximum Will Points. Specter Knight once again starts with 8 Will points, and this is increased by 2 points by finding Willful Wisps, 6 of which are hidden in various stages across The Valley, meaning Specter Knight has a maximum Will Capacity of 20, like Shovel Knight.
Specter Knight also has a cloak that deals with Will Capacity. The Raiment of Risk grants Specter Knight special abilities when he breaks a Checkpoint. When a checkpoint is broken, and Specter Knight is not already boosted by the Raiment, there will be a gem in the middle of the checkpoint. When Specter Knight grabs this gem, his Will Capacity is reduced back to the starting 8 Will points (regardless of his current maximum Will Capacity) in exchange for continually regenerating Darkness and additional reach for his attacks in the form of small fireballs after every strike. These changes are not permanent and will only last until the end of the stage or until Specter Knight dies.
In New Game Plus of Specter of Torment, there are no Will Points, instead Will and Darkness are combined into one giant Darkness Bar, which continually decreases as time goes.