Regeneration

 is a buff granted to the player upon consuming a Regeneration Potion. The buff increases the rate at which your life regenerates by 2 health per second, and lasts for 5 minutes (but can cancelled at any time by right-clicking the icon).

Using a Band of Regeneration or a Charm of Myths or a Celestial Stone or a Sun Stone or a Moon Stone or the Crimson Armor or the Palladium armor will increase life regeneration.