Constitution

Constitution Error creating thumbnail: Unable to save thumbnail to destination
​Constitution : (also known as health, and formerly as Hitpoints or HP) is a skill that affects how many life points (LP) a player or monster has. Life points represent the amount of damage a player or monster can withstand before it dies. Death occurs when a player or monster's life points reach zero.

Training
Anytime you use your combat skills by attacking or defending you gain hitpoint xp.