Game mechanics

Player mechanics

• Adrenaline Meter – The Adrenaline Meter provides a massive damage boost when activated. The meter only fills up during boss fights if the player does not get hit. It is exclusive to Revengeance and Death Mode, unless the player has Draedon's Heart, which adds the Nanomachines meter.
• Difficulty Indicator – The Difficulty Indicator is a UI element that allows the player to change the world difficulty at will if they are in Expert Mode or above and no bosses are alive.
• Flight Time Bar – The Flight Time Bar is a UI element that displays the current percentage of flight time remaining.
• Rage Meter – The Rage Meter provides a damage boost when activated. The meter only fills up if the player is close enough to an enemy or boss. It is exclusive to Revengeance and Death Mode, unless the player has the Shattered Community equipped.

Combat

• Buffs – Buffs are special stats or visual bonuses which are granted to the player after consuming certain items.
• Damage reduction – Damage reduction is a stat that decreases the amount of damage the player or other NPCs receive based on a percentage of damage taken.
• Defense damage – Defense damage makes certain enemy and boss attacks reduce the player's defense and damage reduction on hit.
• Debuffs – Debuffs are temporary, negative status effects. Unlike buffs, they cannot be cancelled for free at any time, and instead require paying the Nurse for cancellation.
• Enchantment – Enchantment is unlocked after defeating Supreme Witch, Calamitas and is a service provided by the Brimstone Witch. It allows players to enchant certain items, providing them with unique additional qualities.
• Stealth – Stealth is exclusive to the Rogue class which comes with its own unique meter. This mechanic allows the player to become slightly invisible when equipping certain rogue armors and allows rogue weapons to perform stealth strikes.

Game

• Lore – The Calamity Mod adds lore-related elements to various aspects of the game such as Lore items.
• Vanilla changes – Vanilla changes made by the Calamity Mod change several aspects and details regarding vanilla Terraria content.

Interface

• Boss Health Bar – The Boss Health Bar displays the percentage of the boss's current health, the name of the boss, and how much health the boss has remaining.
• Cooldown Rack – The Cooldown Rack displays cooldowns for items and actions.
• Speedrun Timer – The Speedrun Timer tracks how long the player has been playing on the current world.

Items

• Charge – Displays the remaining charge of Draedon's Arsenal tools and weapons, which is indicated in their tooltips. The majority of the Draedon's Arsenal equipment also requires charge to function which can be gained via the Charging Station, though it requires Draedon Power Cells to operate.
• Death prevention – Death prevention allows the player to prevent death when taking fatal damage while certain items are equipped.
• Lifesteal – Lifesteal allows certain equipment to heal the player upon damaging enemies.
• Modifier – A Modifier applies changes to an item's statistics. Weapons and accessories have a chance to have modifiers applied at random when they are crafted, appear as loot in chests, or are dropped by enemies. The Calamity Mod adds various new modifiers themed around the Rogue class as well as altering some of vanilla's modifiers.
• Rarity – Rarity is a measure of how difficult to obtain or how valuable an item is, indicated by the color of its name.
• Vanilla item recipes – Vanilla item recipes made by the Calamity Mod make certain vanilla items in the game craftable or add more various materials to already existing recipes.

World

• Revengeance Mode – Revengeance Mode is a world difficulty that serves as an increased challenge compared to Expert Mode. This mode makes various changes to enemy and boss AI and stats along with other general changes, as well as allowing certain bosses to drop exclusive items.
• Death Mode – Death Mode is a world difficulty that serves as an increased challenge compared to Revengeance Mode. This mode makes various changes to enemies and bosses by making them more difficult or increasing their stats further than in Revengeance Mode, along with other general changes and allowing some bosses to drop exclusive items.

Other

• Music – The Calamity Mod adds many new music tracks. Each track will play and loop endlessly while the player is in a specific biome or while certain events are taking place.
• Status messages – Status messages display as chat lines in the lower-left of the game screen when certain conditions apply.