The Iron Heart is an item placed in a newly spawned player's inventory. Upon being used in Expert Mode, it enables or disables several effects on every character in the current world:
- Natural Health regeneration cannot increase beyond 0, preventing the player from naturally healing over time.
- If the player is under effects that decrease life regeneration (such as the Drunk Princess' Drinks, Mana Polarizer, or Ethereal Extorter), life regeneration bonuses are able to offset them up to the point where they deal no damage. Damaging debuffs, however, are unaffected by this, and will deal full damage regardless of the player's hidden life regeneration.
- Recovery Potions cannot be used.
- Direct damage taken by the player now deals a minimum amount of damage, dependent on the player's max HP. The damage floor is calculated as 40 + 10% of the player's max HP. Hits that would deal more damage than this minimum will deal their normal damage.
- The player's life hearts will become light gray in appearance, with black 'eyes' on either side of each, matching the appearance of being heart-shaped skulls. They remain with this appearance even after using Life Fruits or other permanent power-ups.
- The player will have custom hit and death sounds.
- A softer version of the hit sound plays if the taken damage is below (and therefore increased to) the damage floor, and a louder version plays if the damage taken is above the damage floor.
- The Iron Heart's effects are tied to the world it was used in, rather than the player that used it. This means that all players that join a world in which the Iron Heart has been used will have the Iron Heart's effects, even if they don't use the item.
- Hearts, the Nurse, and Lifesteal effects will still heal the player while Iron Heart is active.
- The damage multiplier applied to the player by the Blood Pact's critical hits and the Dimensional Soul Artifact are applied after Iron Heart's damage floor.
- Permafrost's Concoction, the Nebulous Core, and the Draconic Elixir's revive effects can still restore the player to their set health amounts while Iron Heart is active.
- Fall damage, thorny bushes, and (wooden) spikes are unaffected by Iron Heart's damage floor, but Traps are affected.
- The Bloodflare Core can heal the player while Iron Heart is active, as it heals the player directly instead of increasing life regeneration.
- Due to disabled life regeneration, Iron Heart may be used to trigger certain effects that only happen when below certain amount of health such as Necklace of Vexation, or Old Duke's Scales.
- The player can manually lower their health to trigger these effects by using items such as the Thorn Blossom.
- The appearance of the life hearts after using the Iron Heart is a reference to the game Hollow Knight, in which the player's mask-based life meter bears a striking resemblance.
- This item's name is a reference to Hollow Knight's perma-death mode, known as "Steel Soul".
- The life hearts' appearance also references the life hearts in Minecraft's perma-death mode known as "Hardcore", as the mode causes the player's hearts to develop eye-like streaks.
- In previous versions of the mod, this item made dying while a boss is alive permanently kill the player in a similar manner to Hardcore.
- Additionally in previous versions of the mod, this item became unusable after a minute of runtime in the world.
|Combat||Charge • Damage Reduction • Defense damage • Hit Sounds • Immunity frames • Lifesteal • Minions • Proficiency • Rogue|
|Environment||Biome backgrounds • Events • Music • Status messages|
|Events||Acid Rain • Boss Rush|
|Items||Alternative crafting ingredients • Consumable • Crafting stations (By Hand) • Drops • Modifiers • Rarity • Recipes • Vanilla item recipes|
|Game||AI • Armageddon • Boss Health Bar • Configuration options • Death Mode • Defiled Feather • Fishing • Game controls • Iron Heart • Lore • Malice Mode • Revengeance Mode • Vanilla changes|
|Player||Adrenaline Meter • Aggro • Buffs and Debuffs • Death Prevention • Defense • Rage Meter|