The Constitution is the stat affecting your health bar. If your health bar drop to 0, it's GAME OVER.
The formula for calculating your health is:
110 + (20 x Character level) + (20 x Constitution level)
Your starting health is 150 as you start with a character level 1, and Constitution level 1.
Your can get more health by wearing some items such as:
- The Ring of the Spirit: The Lost Ring quest reward.
- The Ring of Life: Can be bought at the Laboratory Shop
- Weapon of Life (suffixe / Multiplayer Only): Gives bonus health