Terraria - Systems
Terraria's systems are the rules that sit around combat and building: world progression flags, the Hardmode conversion, difficulty modes, NPC housing and happiness, reforging, the crafting station ladder, fishing quests, wiring and the event calendar. Most of them interact, so a boss kill can unlock...
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of 12 entries
· updated 2026-09-15
| Name | Type | Description | Stats | Source |
|---|---|---|---|---|
| Boss Progression and World Flags | Progression System | The campaign is a chain of world flags rather than a level curve. | Starts: Eye of Cthulhu, Eater of Worlds or Brain of Cthulhu Gate: Wall of Flesh converts the world to Hardmode Final: Moon Lord after the four Celestial Pillars | Built into world generation and boss summoning |
| Hardmode Conversion | World System | Defeating the Wall of Flesh releases the ancient spirits of light and dark: the Hallow is created, the Corruption or Crimson begins spreading faster, new ore is generated in the world, and the Dungeon, Underworld and Jungle gain Hardmode enemies. | Trigger: Wall of Flesh defeated Spread: Corruption/Crimson and Hallow spread through stone, sand, ice and grass Ore: Cobalt or Palladium, Mythril or Orichalcum, Adamantite or Titanium | Automatic on the Wall of Flesh kill |
| Difficulty Modes (Journey, Classic, Expert, Master) | Difficulty System | World creation picks the difficulty. Journey is a sandbox mode with a difficulty slider, research and duplication; Classic is the standard balance; Expert doubles boss health and adds Expert-exclusive drops and treasure bags; Master makes enemies and bosses far harsher and adds Master-exclusive pets and mounts. | Journey: Creative tools, research and duplication, adjustable difficulty Classic: Standard balance Expert: Bosses with more health, Expert drops and treasure bags Master: Hardest mode with Master-exclusive vanity and pets | Chosen at world creation and fixed for that world |
| Journey Mode | Sandbox Mode | Added in 1.4, Journey Mode adds a research system: collecting enough of an item unlocks it for infinite duplication, and the player can toggle time, weather, spawn rates, infection spread and difficulty. | Research: Collect a set number of an item to unlock duplication Controls: Time, weather, spawn rate, infection spread and difficulty sliders Restriction: Some items and drops are not researchable | Available when a world is created in Journey difficulty |
| NPC Happiness and Pylons | Town System | Since 1.4 each NPC has preferred biomes and neighbours. | Effect: Lower shop prices and pylon access Pylons: One pylon per biome, two NPCs per pylon Penalty: Crowded or mismatched housing raises prices | Built into the 1.4 NPC housing system |
| Reforging and Prefixes | Gear System | The Goblin Tinkerer rerolls a weapon or accessory's modifier for coins. | Vendor: Goblin Tinkerer Cost: Scales with item value Best Rolls: Legendary, Unreal, Mythical for weapons; Warding, Menacing, Lucky for accessories | Unlocked after the Goblin Army event and freeing the Goblin Tinkerer |
| Crafting Station Ladder | Crafting System | Crafting is gated by stations, not by recipes alone: Work Bench to Furnace and Anvil, then Hellforge, then the Hardmode Mythril or Orichalcum Anvil and Adamantite or Titanium Forge, then the Lihzahrd Furnace and the Ancient Manipulator for Lunar gear. | Early: Work Bench, Furnace, Iron or Lead Anvil Hardmode: Mythril or Orichalcum Anvil, Adamantite or Titanium Forge Endgame: Lihzahrd Furnace, Ancient Manipulator | Stations are crafted or found in the world |
| Accessories and Equipment Slots | Gear System | Accessories are the build-defining slot: wings, boots, dash items, damage emblems, mana and ammo savers and the Tinkerer's Workshop combinations all compete for a small number of slots. | Slots: Five by default, six with the Demon Heart in Expert Core: Wings, boots, dash, damage emblem, class-specific accessory Combining: Tinkerer's Workshop merges accessories into single slots | Accessories drop, are found or are crafted throughout the game |
| Fishing and Angler Quests | Side System | Fishing produces fish, crates and quest catches. | Quest Giver: Angler Rewards: Fishing accessories, potions, decorations and the Golden Fishing Rod Crates: Wooden, Iron, Gold and biome crates with ore and loot | Unlocked by finding the Angler at the Ocean and crafting a fishing rod |
| Wiring and Logic | Building System | The Mechanic's wiring system connects switches, pressure plates, timers, actuators and logic gates. | Vendor: Mechanic Components: Wire, wrenches, switches, timers, actuators, sensors, logic gates Uses: Farms, traps, teleporters, automated doors | Unlocked by freeing the Mechanic in the Dungeon and buying wire tools |
| Events and Invasions | Event System | Events run on conditions rather than a calendar: Blood Moons and Solar Eclipses trigger at night or after boss kills, Goblin and Pirate invasions trigger on their own conditions, and the Pumpkin and Frost Moons are summoned with crafted medallions. | Night Events: Blood Moon, Solar Eclipse Invasions: Goblin Army, Frost Legion, Pirate Invasion, Martian Madness Summoned: Pumpkin Moon, Frost Moon, Old One's Army | Triggered by world conditions or summoned with event items |
| Bestiary | Collection System | Added in 1.4, the Bestiary tracks every enemy, critter and NPC the player has killed or seen, with kill counts unlocking entries and percentage milestones. | Tracks: Enemies, critters, NPCs and bosses Rewards: Zoologist stock and the Universal Pylon at 100% Progress: Percentage completion per category | Automatic from 1.4 onward |
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