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Damage Reduction (DR) is a stat that decreases damage received by the player or other NPCs based on a percentage. This is different from defense, which decreases damage by flat values. Each percentage point of DR is additive, incrementing a total value that the damage then gets decreased by.

Player Damage Reduction[]

A graph displaying the relationship between the player's DR stat and the percent of damage that gets reduced in actuality.

The Calamity Mod adjusts the effective percentage of this stat for the player with a diminishing scale, with all DR reducing effects (such as Cursed Inferno) being calculated after it has been scaled. NPC DR is not affected by this diminishing scaling.

The scaling formula is: 1 - 1(1 + dr)

For example, if the player has 25% DR, it will be scaled to 1 - 1(1 + 0.25) = 0.2, or 20% DR.

Certain vanilla items also have their damage reduction boosts adjusted:

List of Damage Reduction Boosts[]

The following include a list of items, buffs, and debuffs added in the Calamity Mod that can increase or decrease damage reduction stat.

Source Damage Reduction (DR) Condition
The CommunityThe Community 1.25% to 5% Depending on bosses killed.
Profaned Soul ArtifactProfaned Soul Artifact 2.5%
5%
0%
When Defensive Guardian is active.
When Offensive Guardian is also active.
If Burnt Out is active, regardless of prior conditions.
Polaris ParrotfishPolaris Parrotfish 1% When Polaris Boost buff is active.
Spirit GlyphSpirit Glyph 3% When Spirit Defense buff is active.
TequilaTequila 3% When Tequila debuff is active during the daytime.
Hallowed RuneHallowed Rune 4% When Hallowed Defense buff is active.
Archaic PowderArchaic Powder 5% While Underground or in the Underworld.
Bloody Worm ToothBloody Worm Tooth 5%
10%
Initially.
When below 50% health.
Craw CarapaceCraw Carapace 5% Always.
Evergreen GinEvergreen Gin 5% When Evergreen Gin debuff is active.
Honey DewHoney Dew 5% While in the Jungle.
Leviathan AmbergrisLeviathan Ambergris 5% When outside of liquid.
Living DewLiving Dew 5% While in the Jungle.
MoonshineMoonshine 5% When Moonshine debuff is active.
Phantomic ArtifactPhantomic Artifact 5% When Phantomic Shield buff is active.
Sea ShellSea Shell 5% When submerged in liquid.
Titan Scale PotionTitan Scale Potion 5%
15%
When Titan Scale buff is active.
10 seconds after a true melee strike during the buff.
Yharim's StimulantsYharim's Stimulants 6% When Yharim's Power buff is active.
Ambrosial AmpouleAmbrosial Ampoule 7% Always.
AfflictionAffliction 7% While equipped or when Afflicted buff is active
Corrupt FlaskCorrupt Flask 7% While in the Corruption.
Crimson FlaskCrimson Flask 7% While in the Crimson.
Tequila SunriseTequila Sunrise 7% When Tequila Sunrise debuff is active during the daytime.
Core of the Blood GodCore of the Blood God 8% Always.
The AbsorberThe Absorber 10%
15%
Initially.
When submerged in liquid.
Blazing CoreBlazing Core 10% Always.
Bloody Worm ScarfBloody Worm Scarf 10% Always.
GraxGrax 10% When Grax Boost buff is active.
The SpongeThe Sponge 15%
20%
Initially.
When submerged in liquid.
Frigid BulwarkFrigid Bulwark 15%
20%
When below 50% health.
When below 15% health.
Rampart of DeitiesRampart of Deities 15%
20%
When below 50% health.
When below 15% health.
IrradiatedIrradiated -10% Always
Void of CalamityVoid of Calamity -10% Always.
Corruption EffigyCorruption Effigy -20% When Corruption Effigy buff is active.
Vulnerability HexVulnerability Hex -10% Always.

Alternative Damage Reduction[]

Alternative damage reduction is a hidden player statistic separate from normal damage reduction. It directly modifies damage taken, and is affected differently by the scaling formula. The following tables show a list of damage reductions that are additive of each other, including sources inflicted to the player and external sources such as enemy debuffs.

Player Sources[]

Source Damage Reduction Contact Projectile Notes
BannersBanners 75% / 50% Tango Cross1.png Tango Tick1.png While the player is in range.
Abyssal Diving SuitAbyssal Diving Suit 0-15% Tango Tick1.png Tango Tick1.png When damage taken is above 50 while the Abyssal Diving Suit Plates buff is active.
Reduces by 3% as more hits are taken, up to three times where the plates are broken and DR reduces to 0%.
Triumph PotionTriumph Potion 0-15% Tango Tick1.png Tango Cross1.png Varies based on enemy health.
The EvolutionThe Evolution 15% Tango Cross1.png Tango Tick1.png When struck by a projectile that has been previously reflected.
The TransformerThe Transformer 50% Tango Tick1.png Tango Tick1.png Only reduces damage taken from electrical attacks and enemy bullets.
A list of attacks can be seen here.
Core of the Blood GodCore of the Blood God
Flesh TotemFlesh Totem
50% Tango Tick1.png Tango Cross1.png Effect has a 20-second cooldown.
Auric Tesla armorAuric Tesla armor (Royal Helm)
Tarragon armorTarragon armor (Helm)
50% Tango Tick1.png Tango Cross1.png While the Tarragon Cloak set bonus buff is active.
Effect has a 30-second cooldown.
Auric Tesla armorAuric Tesla armor (Royal Helm)
Bloodflare armorBloodflare armor (Ram Mask)
50% Tango Tick1.png Tango Cross1.png While the Blood Frenzy set bonus buff is active.
Effect has a 30-second cooldown.
Honey DewHoney Dew 25% Tango Tick1.png Tango Tick1.png Only reduces damage taken from bees, hornets, and their projectiles.
A list of attacks can be seen here.
Eskimo armorEskimo armor 10% Tango Tick1.png Tango Cross1.png Only reduces damage taken from ice-based attacks.
Trinket of ChiTrinket of Chi 15% Tango Tick1.png Tango Tick1.png While the Chi buff is active.
Fearmonger armorFearmonger armor 15% Tango Tick1.png Tango Tick1.png During the Pumpkin Moon or Frost Moon while no bosses are alive.
Aquatic HeartAquatic Heart 20% Tango Tick1.png Tango Tick1.png While the Ice Shield buff is active.
Phantomic ArtifactPhantomic Artifact 20% Tango Cross1.png Tango Tick1.png When struck with the Phantomic Bulwark active.
Permafrost's ConcoctionPermafrost's Concoction 30% Tango Tick1.png Tango Tick1.png While the Encased buff is active.
Effect has a 3-minute cooldown.
Daedalus armorDaedalus armor (Helm) 50% Tango Cross1.png Tango Tick1.png When reflecting a projectile.
Lion HeartLion Heart 50% Tango Tick1.png Tango Tick1.png When the energy shell is active while the weapon is held.
The BeeThe Bee 50% Tango Tick1.png Tango Tick1.png When at full health with a 10-second cooldown.
Revengeance ModeRevengeance Mode 20% Tango Tick1.png Tango Tick1.png Before any boss is defeated.
Adrenaline MeterAdrenaline Meter 50-65% Tango Tick1.png Tango Tick1.png When taking damage while the meter is full.
Each of Adrenaline's permanent power-ups increases value by 5%, to a maximum of 65%.
Onyx Excavator KeyOnyx Excavator Key
Tundra LeashTundra Leash
10% Tango Tick1.png Tango Tick1.png When moving over half of the mount's top speed while mounted.
Vulnerability HexVulnerability Hex -30% Tango Tick1.png Tango Tick1.png While the player is inflicted with this debuff.
IrradiatedIrradiated -10% Tango Tick1.png Tango Tick1.png While the player is inflicted with this debuff.
Corruption EffigyCorruption Effigy -20% Tango Tick1.png Tango Tick1.png While the player is in range.
Void of CalamityVoid of Calamity -15% Tango Tick1.png Tango Tick1.png n/a

Non-Player Sources[]

Source Damage Reduction Contact Projectile Notes
Temporal SadnessTemporal Sadness 50% Tango Tick1.png Tango Cross1.png While enemies are inflicted with this debuff.
Relic of ResilienceRelic of Resilience 45% Tango Tick1.png Tango Cross1.png While enemies contact the shards of the bulwark.
Web spitWeb Spit (Black Recluse)
Pink LaserPink Laser (Astral Probe, Gastropod, Probe)
Ice BoltFrost Blast (Ice Clasper, Ice Elemental)
Ice BoltRune Blast (Rune Wizard)
Golden Shower (projectile)Golden Shower (Ichor Sticker)
Nimbus Rain (projectile)Nimbus Rain (Angry Nimbus)
Hornet StingerStinger (Hornet)
Flaming ArrowFlaming Arrow (Skeleton Archer)
Bullet (projectile)Deadeye Bullet (Pirate Captain, Pirate Deadeye, Tactical Skeleton)
CannonballCannonball (Pirate Captain)
25% Tango Cross1.png Tango Tick1.png Only in Expert Mode and Hardmode before any Hardmode boss is spawned

Calculation[]

After the total damage reduction is calculated, several effects may take place that will modify this stat:

  • If the player is inflicted with Armor Crunch, the final value is multiplied by 0.33.
  • If the player is inflicted with War Cleave, the final value is multiplied by 0.75.
  • If the player has normal DR stat, the final value is multiplied by (1 - DR). The DR stat used is calculated after being accounted for regular DR scaling.
  • After all calculations, the final value is scaled using the same formula as the normal DR stat: 1 - 1(1 + dr)

For example, if a player receives 200 contact damage from an enemy inflicted by Temporal Sadness while under the effects of Blazing Core, Bloody Worm Scarf, Corruption Effigy, Endurance Potion, and War Cleave.

  • First, all sources of contact damage reduction are added, including Temporal Sadness and Corruption Effigy, totaling 50% - 20% = 30%.
  • Next, the value is multiplied by War Cleave's multiplier, totaling 30% * 0.75 = 22.5%.
  • Then, the normal DR from Blazing Core, Bloody Worm Scarf, Corruption Effigy, and Endurance Potion is accounted. The player's unscaled normal DR is 10% + 10% + 10% - 20% = 10%, and final normal DR is (1 - 1 / (1 + 0.10)) * 100% = 9.09%.
  • Therefore, the alternative DR reduces to 22.5% * (1 - 0.0909) = 20.45%.
  • Finally, the alternative DR goes through scaling and results in a final alternative DR of (1 - 1 / (1 + 0.2045)) * 100% = 16.98%.
  • In the end, the player will take 200 * (1 - 0.0909) * (1 - 0.1698) = 151 damage.

Enemy Damage Reduction[]

Unlike player damage reduction, enemy damage reduction is a stat not available in vanilla, but rather added by the Calamity Mod to various NPCs including vanilla ones. Similar to the player, the enemy DR is calculated after defense.

Certain debuffs can reduce enemy damage reduction:

  • Kami Flu has a damage reduction multiplier of 0.8x.
  • Cursed Inferno has a damage reduction multiplier of 0.8x.
  • War Cleave has a damage reduction multiplier of 0.75x.
  • Betsy's Curse has a damage reduction multiplier of 0.66x.
  • Marked has a damage reduction multiplier of 0.5x.

Certain enemies such as enraged Supreme Calamitas and the Dungeon Guardian have a 99.9999% damage reduction, effectively taking 1/1,000,000 of the original damage dealt. These enemies' damage reduction cannot be altered by any debuffs.

List of NPCs with Damage Reduction[]

Calamity NPCs[]

  • Image NPC DR
    Jungle Dragon, Yharon Jungle Dragon, Yharon 22%
    Desert Scourge Body Desert Scourge Body 5%
    Desert Scourge Tail Desert Scourge Tail 10%
    The Devourer of Gods Body The Devourer of Gods Body 92.5%
    The Devourer of Gods Body The Devourer of Gods Body (Final Phase) 92.5%
    The Leviathan The Leviathan 35%
    Anahita Anahita 20%
    Ice Shield Ice Shield 50%
    The Plaguebringer Goliath The Plaguebringer Goliath 30%
    Earth Elemental Earth Elemental 10%
    Cloud Elemental Cloud Elemental 5%
    Cryogen Cryogen 10%
    Cryogen's Shield Cryogen's Shield 40%
    Calamitas Calamitas 15%
    Catastrophe Catastrophe (Brother of Calamitas) 15%
    Cataclysm Cataclysm (Brother of Calamitas) 15%
    Providence, the Profaned Goddess Providence, the Profaned Goddess 30%
    Profaned Guardian Profaned Guardian (Offense) 30%
    Profaned Guardian Profaned Guardian (Defense) 40%
    Profaned Guardian Profaned Guardian (Healer) 20%
    Brimstone Elemental Brimstone Elemental (Phase 1) 15%
    Brimstone Elemental Brimstone Elemental (Phase 2) 15%
    Brimstone Elemental Brimstone Elemental (Phase 3) 15%
    Storm Weaver Head Storm Weaver Head (Armored) 99.99%
    Storm Weaver Body Storm Weaver Body (Armored) 99.99%
    Ceaseless Void Ceaseless Void 50%
    Profaned Guardian Profaned Guardian (Main) 30%
    Profaned Guardian Profaned Guardian (Rock) 40%
    Profaned Guardian Profaned Guardian (Crystal) 20%
    The Dragonfolly The Dragonfolly 10%
    Supreme Calamitas Supreme Calamitas (Phase 1) 25%
    Supreme Calamitas Supreme Calamitas (Phase 2) 25%
    Catastrophe Catastrophe (Brother of Supreme Calamitas) 25%
    Cataclysm Cataclysm (Brother of Supreme Calamitas) 25%
    Despair Stone Despair Stone 35%
    Soul Slurper Soul Slurper 15%
    Profaned Energy Profaned Energy 10%
    Scorn Eater Scorn Eater 5%
    Cnidrion Cnidrion 5%
    Astrum Deus Head Astrum Deus Head 20%
    Astrum Deus Body Astrum Deus Body 10%
    Astrum Deus Tail Astrum Deus Tail 30%
    Ravager Head Ravager Head 15%
    Ravager Body Ravager Body 35%
    Ravager Claw Ravager Claw 15%
    Ravager Leg Ravager Leg 15%
    Ravager Head Ravager Head (Phase 2) 15%
    Rock Pillar Rock Pillar 30%
    Flame Pillar Flame Pillar 20%
    Shockstorm Shuttle Shockstorm Shuttle 15%
    Sand Tortoise Sand Tortoise 25%
    Astral Probe Astral Probe 15%
    Armored Digger Head Armored Digger Head 15%
    Armored Digger Body Armored Digger Body 25%
    Armored Digger Tail Armored Digger Tail 35%
    Polterghast Polterghast (Phase 1) 15%
    Necroghast Necroghast (Phase 2) 20%
    Necroplasm Necroplasm (Phase 3) 50%
    Polterghast Polterghast (Clone) 10%
    Phantom Phantom 10%
    Soul Seeker Soul Seeker 10%
    Soul Seeker Soul Seeker (Supreme) 25%
    Plaguebringer Plaguebringer 20%
    Sepulcher Head Sepulcher Head 99.99%
    Sepulcher Body Sepulcher Body 99.99%
    Sepulcher Body Sepulcher Body (Weak) 99.99%
    Sepulcher Tail Sepulcher Tail 99.99%
    Colossal Squid Colossal Squid 5%
    Mauler Mauler 5%
    Aquatic Scourge Head Aquatic Scourge Head 5%
    Aquatic Scourge Body Aquatic Scourge Body 10%
    Aquatic Scourge Body Aquatic Scourge Body (Alternate) 10%
    Aquatic Scourge Tail Aquatic Scourge Tail 15%
    Bobbit Worm Bobbit Worm 25%
    Cryon Cryon 10%
    Phantom Debris Phantom Debris 10%
    Overloaded Soldier Overloaded Soldier 15%
    Brimling Brimling 15% (Normal) / 60% (Boosted)
    Great Sand Shark Great Sand Shark 25%
    Eidolon Wyrm Head Eidolon Wyrm Head 15%
    Eidolon Wyrm Body Eidolon Wyrm Body 0%
    Eidolon Wyrm Tail Eidolon Wyrm Tail 0%
    Adult Eidolon Wyrm Head Adult Eidolon Wyrm Head 40%
    Adult Eidolon Wyrm Body Adult Eidolon Wyrm Body 0%
    Eidolon Wyrm Body Eidolon Wyrm Body (Alternate) 0%
    Adult Eidolon Wyrm Tail Adult Eidolon Wyrm Tail 0%
    Astrum Aureus Astrum Aureus 50%
    Big Sightseer Big Sightseer 15%
    Small Sightseer Small Sightseer 15%
    Aries Aries 15%
    Atlas Atlas 15%
    Mantis Mantis 15%
    Nova Nova 15%
    Astralachnea Astralachnea 15%
    Astralachnea Astralachnea (On Wall) 15%
    Hive Hive 15%
    Stellar Culex Stellar Culex 15%
    Fusion Feeder Fusion Feeder 15%
    Hadarian Hadarian 15%
    Giant Clam Giant Clam 30%
    Prism-Back Prism-Back 25%
    Blinded Angler Blinded Angler 20%
    Clam Clam 25%
    Eutrophic Ray Eutrophic Ray 5%
    Crown Jewel Crown Jewel 10%
    Skyfin Skyfin 5% (Tier 2 & 3)
    Nuclear Terror Nuclear Terror 30%
    The Old Duke The Old Duke 50% / 0%
    Cragmaw Mire Cragmaw Mire 0-50%
    Gamma Slime Gamma Slime 15%
    Orthocera Orthocera 7.5% (Tier 2)
    15% (Tier 3)
    Acid Eel Acid Eel 5% (Tier 3)
    Trilobite Trilobite 25%
    Flak Crab Flak Crab 20% (Tier 3)
    Sulphurous Skater Sulphurous Skater 15% (Tier 3)
    XF-09 Ares XF-09 Ares (Body) 35%
    XF-09 Ares Gauss Nuke XF-09 Ares Gauss Nuke 35%
    XF-09 Ares Laser Cannon XF-09 Ares Laser Cannon 35%
    XF-09 Ares Plasma Cannon XF-09 Ares Plasma Cannon 35%
    XF-09 Ares Tesla Cannon XF-09 Ares Tesla Cannon 35%
    XS-01 Artemis XS-01 Artemis (First Phase) 25%
    XS-03 Apollo XS-03 Apollo (First Phase) 25%
    XS-01 Artemis XS-01 Artemis (Second Phase) 25%
    XS-03 Apollo XS-03 Apollo (Second Phase) 25%
    XM-05 Thanatos Head XM-05 Thanatos Head 99.99% / 0%
    XM-05 Thanatos Body XM-05 Thanatos Body 99.99% / 0%
    XM-05 Thanatos Tail XM-05 Thanatos Tail 99.99% / 0%
  • Vanilla NPCs[]

     
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    Reactive Damage Reduction[]

    Every boss from both Vanilla Terraria and the Calamity Mod has a value associated with it that represents a rough estimate of how long it should take to kill outside of the Boss Rush, timed from when it spawns. If the player appears to be dealing too much damage within the intended kill time, then the boss gains extra DR. This DR gain is calculated after everything else, meaning it cannot be affected by debuffs.

    This mechanic takes into account the time elapsed and the boss's health. The time elapsed is divided by kill time for the Time Ratio value, while the boss's current health is divided by its total health for the Health Ratio value. Reactive DR does not apply under the following conditions:

    • If the sum of the two aforementioned values is greater than or equal to 1
    • There is no kill time value assigned
    • The player is in Boss Rush.
    • Any boss of the higher assigned tier is defeated. If the boss is in tier 6, defeating it will permanently disable Reactive DR for that boss.

    In addition, there is a Scale Factor that varies on certain conditions. The default value of the multiplier is 1.5, which increases to 2 in Malice Mode. Certain bosses have a higher multiplier, including:

    In Normal Mode and Expert Mode, the scale factor is multiplied by 0.67 and 0.85 respectively.

    The damage reduction gained is based on a boss's Base DR, which is prior to any other effects such as debuffs. Using the four values mentioned, the total amount of damage reduction gained is equal to: [(1 - Base DR) * Scale Factor] - [(1 - Base DR) * Scale Factor](2 - Time Ratio - Health Ratio)

    For example, suppose Cryogen reaches 30% health within 36 seconds while it is inflicted with the Cursed Inferno debuff, in Revengeance Mode:

    • Cryogen's base DR is 10% or 0.10.
    • The multiplier is equal to 1.5, as it is not in Malice Mode.
    • Cryogen's kill time value is 180 seconds. As such, the time ratio is equal to 36 / 180 = 0.20.
    • The health ratio is equal to 30% or 0.30.
    • Therefore, the amount of reactive DR gained is equal to (1 - 0.10) * 1.5 - (1 - 0.10) * 1.5(2 - 0.20 - 0.30) = 1.35 - (1.35 / 1.50) = 0.45 or 45%.
    • Cryogen is also affected by Cursed Inferno, which multiplies damage reduction by 0.8x, from 10% to 8%.
    • The two values combine into a total, instantaneous damage reduction of 53%.

    Timed Aggression[]

    All bosses in Revengeance Mode or higher become more aggressive and enter their later phases regardless of their current HP if the player takes too long to defeat them. The condition for this to activate is for the player to be calculated to take 50% longer than the expected kill time, or higher.

    For example, King Slime has an expected kill time of 60, and summons the Crown Jewel at 50% of its health. This means it is expected that King Slime will summon the Crown Jewel at 30 seconds into the fight. However, if the player takes at least 50% longer (i.e. King Slime is still not below 50% at 45 seconds into the fight), it will enter that phase regardless, and summon the Crown Jewel.

    Kill Time Table[]

    The following includes the kill time values for each boss. Several bosses have multiple values for different phases.

    Boss Tier Kill Time (seconds)
    King Slime 1 60
    Desert Scourge 1 60
    Eye of Cthulhu 1 90
    Crabulon 1 90
    Eater of Worlds 1 120
    Brain of Cthulhu (Creepers) 1 30
    Brain of Cthulhu 1 90
    The Hive Mind 1 120
    The Perforator Hive 1 120
    Queen Bee 1 120
    Skeletron 1 120
    The Slime God (Slimes) 1 90
    The Slime God (Core) 1 180
    Wall of Flesh 1 120
    Cryogen 2 180
    The Twins 2 180
    Brimstone Elemental 2 180
    The Destroyer 2 180
    Aquatic Scourge 2 120
    Skeletron Prime 2 180
    Calamitas 2 240
    Plantera 2 180
    Leviathan and Anahita 3 180
    Astrum Aureus 3 180
    Golem 3 150
    The Plaguebringer Goliath 3 180
    Duke Fishron 3 150
    Ravager 3 180
    Lunatic Cultist 3 150
    Astrum Deus (Phase 1) 3 60
    Astrum Deus (Phase 2) 3 120
    Moon Lord (Head & Hands) 3 120
    Moon Lord (Core) 3 240
    Profaned Guardians 4 90
    The Dragonfolly 4 120
    Providence, the Profaned Goddess 4 240
    Ceaseless Void (Dark Energies) 5 20
    Ceaseless Void 5 180
    Storm Weaver 5 135
    Signus, Envoy of the Devourer 5 120
    Polterghast 5 180
    The Old Duke 5 180
    The Devourer of Gods (Phase 2) 5 240
    Jungle Dragon, Yharon 6 255
    Exo Mechs 6 360
    Supreme Calamitas 6 300
    Adult Eidolon Wyrm 6 300

    Trivia[]

    • The kill time-based Damage Reduction system is inspired by a similar mechanic from The Binding of Isaac: Rebirth.
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