Health

Hearts are containers, not fixed units. A red heart holds 20 health and a gold one holds 25, so the same full row of twenty icons can mean 400 or 500 depending on how far through the upgrade path you are. The bar empties from the right. If the icons are hard to read mid-fight, the Health and Mana Style setting offers six layouts and three of them print the raw number instead of asking you to count hearts.

You start at 100. Life Crystals add 20 each and stop working after fifteen of them, at 400. From there Life Fruit upgrades hearts instead of adding them, converting each red heart to gold for another 5, and twenty of those takes you to 500. That is the permanent ceiling.

A Lifeforce Potion stacks a temporary 100 on top for 600, which is the highest number the game will ever show you. The detail worth knowing before you go looking is that Life Fruit does nothing at all until you are already at 400, so collecting them early is fine but eating them early is not possible.

Several parts of the world check your maximum health before they will happen at all, which catches out anyone who skipped crystals in favor of exploring:

• 120 before the Nurse will move in.
• 140 before Blood Moons can occur.
• 160 before Slime Rains can occur.
• 200 before the Eye of Cthulhu or Deerclops will show up on their own, and before a Goblin Army will invade unprompted.
• 300 before the Old Man stops telling you that you are not ready for Skeletron, though you can fight it earlier if you insist.

Most of these have other conditions layered on as well, but the health check is the one people forget. If a world feels strangely quiet and no events are firing, count your crystals before you start looking for a bug.

Hearts dropped by enemies restore 20 apiece with no cooldown attached, which makes them the main source of sustain in any long fight. It is also the reason a busy arena is sometimes safer than an empty one: more enemies means more drops, and a steady trickle of hearts outpaces a lot of incoming chip damage.

Potions do more per use but every healing item shares Potion Sickness, 60 seconds by default and 45 with a Philosopher's Stone or Charm of Myths equipped. That reduction is bigger than it reads. Over a five minute boss fight it is one extra full heal, which is often the whole fight.

The Nurse is the third option, a complete heal plus most debuffs cleared for a fee that scales with how much damage you have taken and how many debuffs you are carrying. She is cheapest when you are barely hurt and brutally expensive when you crawl to her at 20 health, which inverts the instinct most people have about when to use her. Parking her next to an arena and topping up early and often is the efficient pattern.

Defense and damage reduction shrink each incoming hit, and they compound with everything else, so they are usually the better investment early. Worth knowing: every accessory can roll a modifier worth up to 4 defense on top of whatever it already does, so a fully reforged loadout is a meaningful block of free defense that costs only money.

Lifesteal works the other way, converting your damage output into health. Vampire Knives and the Spectre Hood set bonus both pay a fraction of what you deal, so they scale with your gear and give you nothing while you are unable to land hits. The Bat Bat returns a flat 1 per strike and is not lifesteal in the technical sense, which only matters because effects that modify lifesteal do not touch it.