Brain of Cthulhu

Type	Flying Enemy
Environment	The Crimson
Damage	20 / 36 / 64 / 54 / 97
Max Life	100 / 170 / 216
Defense	10
KB Resist	20% / 28% / 36%
Immune to
Cold	Vulnerable
Water	-
Sickness	Vulnerable
Electricity	-
Heat	Vulnerable

Type	Boss
Environment	The Crimson
Damage	30 / 54 / 64 / 81 / 97
Max Life	1250 / 2125 / 3718 / 2709 / 4740
Defense	14 (21 while spinning)
KB Resist	50% / 55% / 60%
Immune to
Cold	Vulnerable
Water	-
Sickness	Vulnerable
Electricity	-
Heat	Vulnerable
Coins	5

Type	Boss
Environment	The Crimson
Damage	30 / 54 / 64 / 81 / 97
Max Life	1250 / 2125 / 3718 / 2709 / 4740
Defense	14
KB Resist	50% / 55% / 60%
Immune to
Cold	Vulnerable
Water	-
Sickness	Vulnerable
Electricity	-
Heat	Vulnerable
Coins	5

If you were looking for the Brain of Cthulhu on the vanilla wiki, click here.

"...A product of the folly of the Gods"

The Brain of Cthulhu is a Pre-Hardmode boss that is intended to be fought after Crabulon.

It is the Crimson counterpart to the Eater of Worlds.

While in Revengeance and Death Mode, the Brain of Cthulhu has a buffed AI that is much stronger and more complex than the fight in Classic and Expert Modes.

Spawn

The Brain of Cthulhu is summoned by destroying 3 Crimson Hearts in the Underground Crimson. The player can also use the Bloody Spine in the Crimson. It can be summoned at any time.

Behavior

The Brain of Cthulhu has 20 / 30 / 30 Creepers.

In Revengeance Mode

The Brain of Cthulhu has a spawn animation which changes depending on if the boss is summoned by destroying Crimson Hearts or using Bloody Spine, and two phases in Revengeance and Death Mode. This page will not be covering Classic or Expert Modes for the Brain of Cthulhu. If the Brain of Cthulhu is led outside of the Crimson, it will enrage, causing both the Brain and its Creepers to become much faster. It is less aggressive when fought in the Underground Crimson.

The Brain and the Creepers are capable of inflicting multiple debuffs upon contact damage.

Debuff	Duration	Chance (Brain)	Chance (Creepers)
Debuff	Bleeding	3.75 - 7.5 seconds	11/243	11/81
Broken Armor	4.875 - 9.75 seconds	11/243	11/81
Confused	0.75 - 1.5 seconds	2/243	2/81
Cursed	0.375 - 0.75 seconds	2/243	2/81
Darkness	1.5 - 3 seconds	11/243	11/81
Poisoned	2.625 - 5.25 seconds	11/243	11/81
Silenced	0.75 - 1.5 seconds	11/243	11/81
Slow	2.625 - 5.25 seconds	11/243	11/81
Weak	5.625 - 11.25 seconds	11/243	11/81

Phase 1

In the first phase of the fight, the Brain itself will now attempt to target the player with the lowest aggro, and will prioritize players with low health in multiplayer. No longer enrages on the surface, and now despawns when outside the Crimson instead of enraging. Now has a visual shield effect while Creepers are alive. While Creepers are alive, can perform several different attacks in a randomized order:

Sends out Creepers to opposite sides of the player, then launches them into each other.
Positions itself over the player, then swoops Creepers at the player while raining ichor shots from underneath it.
Arranges Creepers into lines around it, then makes the Creeper lines spin around with an escalating speed.
Spins Creepers around the player, with groups of Creepers occasionally swooping in from the circle at the player.
If few enough Creepers remain, it will stop doing other attacks and isolate the remaining Creepers, while launching Crimson enemies at the player through telekinesis.
When all Creepers are killed, the Brain is stunlocked for several seconds and can be freely damaged. Afterwards, it will respawn its Creepers, with all Creeper attacks upgraded.

Unlike in lower difficulties, Creepers do not drop Crimtane Ores or Tissue Samples when killed.

Phase 2

After killing Creepers twice or if the Brain reaches 50% health, it will enter its second phase. No longer passively creates illusions during second phase. During the second phase, can perform several different attacks in a randomized order:

Charges towards the player before teleporting away.
Flies over the player in a semi-circular motion while raining ichor shots and spawning horizontally traveling blood shots. Afterwards, charges down at the player while leaving blood scythes that move outwards.
Rapidly teleports around the player while firing rings of blood scythes, then flies over them while raining ichor shots.
Creates illusions which spin around the player alongside the real Brain, then fake a charge attack before the real Brain reappears near the player and charges.
Fades away, then creates a large swarm of illusions which orbit around the player, with multiple different appearances. Hitting the real Brain immediately ends the attack, but hitting an illusion or taking too long to hit the real Brain inflicts Burning Blood and Confused on the player.

In Death Mode

Phase 2 will start at 75% health.
All abilities mentioned in Revengeance are 25% faster.

During the Boss Rush

Max health increased to 1,000,000 / 1,700,000 / 2,720,000
Moves and teleports much faster the less Creepers there are remaining.
Movement speed and teleportation greatly increased and increases further at lower health.
Creepers movement speed and acceleration greatly increased.

Summons

Resistances

Creepers take reduced damage from most non-minion piercing projectiles. Each hit decreases the damage of the next hit by 12%, until the eighth hit onwards which deal 20% of original damage.
Creepers take 20% damage from grenade-type projectiles. A list of affected projectiles is below.

Resisted grenades
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Creepers take 50% damage from the Demon Scythe and true melee hits.

Tips

For more elaborate strategies on defeating the Brain of Cthulhu, including weapon and arena recommendations, see Guide:Brain of Cthulhu strategies.

If being fought in the Underground Crimson, it is wise to place platforms in the center of a Crimson chasm as they are usually the largest area in the underground and will allow for more movement.
Piercing weapons are useful for the first phase as they will allow you to damage multiple Creepers at once.
Lighting up your arena will help alleviate some of the effect from the Darkness debuff.

Trivia

If the Vanilla Calamity Mod Music is enabled, the vanilla Boss 3 theme will be replaced with Madness Incarnate, which was composed by Heart Plus Up! and SkippyZii.

History

edit

These history sections are still a work-in-progress, and may not yet contain changes relevant to the current version of the Calamity Mod.

2.1.2:
- No longer deals contact damage while stunned, while transitioning to phase 2, during the downtime between charges, during the semi-circular ichor rain and blood shot attack, while spinning around the player during the Illusion Spin attack, or while invisible after fading out before the Illusion Trick attack.
- Decreased how fast Creepers spin around during the Creeper orbit attack in the second Creeper phase.
- Decreased how much ichor is released by the semi-circular ichor rain and blood shot attack. Attack now additionally fires blood bombs which can be hit with weapons at close-range to redirect them back at the Brain, dealing damage.
- Illusion Spin attack now waits longer before firing blood shots after illusions charge, fires the blood shots behind it instead of in front of it, and it now fires less blood shots in Revengeance Mode.
- Projectiles spawned from projectiles that ignore Illusion Brains will now also ignore Illusion Brains.
- Hitting an Illusion Brain now has an 8-frame delay before damaging and debuffing the player. Hitting the real Brain during this delay prevents this.
- Fixed Adrenaline being able to charge during its spawn animation.
- Fixed Creeper crush attack lasting shorter than intended in Death Mode.
- Fixed Creeper orbit attack rarely causing more Creepers to attack at once than intended.
- Fixed blood scythes not drawing if the Afterimages configuration option is disabled.
- Fixed hitting Illusion Brains not syncing properly in multiplayer.

2.1.1:
- Now always charges twice in second phase instead of charge amount scaling as health lowers.
- Decreased how long the semi-circular ichor rain and blood shot attack in second phase lasts for.
- Changed how Illusion Trick illusion drawing works while using a texture pack.
- Hitting an illusion brain now adds 5 seconds of Burning Blood instead of 10, and Burning Blood duration is now capped at 1 minute.
- Hitting an illusion now deals 50 damage to the player which cannot be reduced by defense. Failing to hit the real brain during the Illusion Trick attack now deals 100 damage to the player which cannot be reduced by defense.
- Can no longer despawn during its death animation.
- Fixed tendril system in Revengeance Mode causing exceptions when spawned outside of Revengeance Mode.
- Fixed visual errors with enemy telekinesis in multiplayer.
- Attempted to fix it sometimes not dropping loot in multiplayer.

2.1.0:
- Nerfed health from 1500 / 2550 / 4207 / 3251 / 5364 to 1250 / 2125 / 3718 / 2709 / 4740 , and Creeper's health from 100 / 170 / 238 / 216 / 302 to 100 / 170 / 216 .
- Nerfed contact damage from 36 / 54 / 81 / 108 / 162 to 30 / 54 / 64 / 81 / 97 , and blood shot damage from 60 / 76 / 114 to 48 / 72 . Nerfed Creeper's contact damage from 24 / 36 / 66 / 96 / 144 to 20 / 36 / 64 / 54 / 97 .
- No longer receives AI changes in Classic and Expert Mode.
- It and Creepers no longer inflict any debuffs on contact in Expert Mode.
- Reworked Revengeance Mode AI:
  - Now has a spawn animation which changes depending on if the boss is summoned by destroying Crimson Hearts or using Bloody Spine.
  - Now attempts to target the player with the lowest aggro, and will prioritize players with low health in multiplayer.
  - No longer enrages on the surface, and now despawns when outside the Crimson instead of enraging.
  - Now has a visual shield effect while Creepers are alive.
  - While Creepers are alive, can perform several different attacks in a randomized order:
    - Sends out Creepers to opposite sides of the player, then launches them into each other.
    - Positions itself over the player, then swoops Creepers at the player while raining ichor shots from underneath it.
    - Arranges Creepers into lines around it, then makes the Creeper lines spin around with an escalating speed.
    - Spins Creepers around the player, with groups of Creepers occasionally swooping in from the circle at the player.
    - If few enough Creepers remain, it will stop doing other attacks and isolate the remaining Creepers, while launching Crimson enemies at the player through telekinesis.
  - When all Creepers are killed, the Brain is stunlocked for several seconds and can be freely damaged. Afterwards, it will respawn its Creepers, with all Creeper attacks upgraded.
  - After killing Creepers twice or if the Brain reaches 50% health, it will enter its second phase. No longer passively creates illusions during second phase.
  - During the second phase, can perform several different attacks in a randomized order:
    - Charges towards the player before teleporting away.
    - Flies over the player in a semi-circular motion while raining ichor shots and spawning horizontally traveling blood shots. Afterwards, charges down at the player while leaving blood scythes that move outwards.
    - Rapidly teleports around the player while firing rings of blood scythes, then flies over them while raining ichor shots.
    - Creates illusions which spin around the player alongside the real Brain, then fake a charge attack before the real Brain reappears near the player and charges.
    - Fades away, then creates a large swarm of illusions which orbit around the player, with multiple different appearances. Hitting the real Brain immediately ends the attack, but hitting an illusion or taking too long to hit the real Brain inflicts Burning Blood and Confused on the player.
  - Now has a death animation.
- Decreased extra Crimtane Ore drop amount in Revengeance Mode from 100-180 to 70-90, and extra Tissue Sample drop amount from 60-120 to 20-30.
- Brain of Confusion now only drops in Expert Mode again.
- Creepers now take 75% damage from true melee weapons instead of 50%, and 33% damage from grenade-type projectiles instead of 20%.
- Rewrote its bestiary entry.

2.0.4.003:
- Now only swaps targets after teleporting or when entering phase 2.
- Blood shots now have a shorter trail.
- Decreased Creeper's enrage scale boost when outside the Crimson from 2 to 1, and enrage scale during Boss Rush from 4 to 2.
- Halved how much Creeper velocity scales with the number of Creepers alive, but scaling velocity from number of Creepers alive is now affected by enrage scale.

2.0.4.002: Buffed contact damage in Master Mode from 135 to 162 , and Creeper's damage from 120 to 144 . Buffed blood shot damage from 108 to 114 .

2.0.4.001:
- Buffed health from 1500 / 2550 / 3060 / 3251 / 3901 to 1500 / 2550 / 4207 / 3251 / 5364 , and Creeper's health from 100 / 170 / 187 / 216 / 238 to 100 / 170 / 238 / 216 / 303 .
- Buffed contact damage from 30 / 54 / 81 / 99 / 135 to 36 / 54 / 81 / 108 / 135 , and Creeper's damage from 20 / 36 / 54 / 72 / 90 to 24 / 36 / 66 / 96 / 120 .
- Now turns the Calamity Boss Health Bar red when enraged outside of Revengeance Mode.
- No longer uses a global scaling contact damage formula based on boss velocity.
- Decreased Creeper amount from 25 / 30 to 20 / 30 , in the For the worthy seed from 40 to 35, and in Legendary Mode from 50 to 40.
- No longer deals contact damage during phase 1, and Creepers no longer deal contact damage while not charging in all difficulties.
- Creepers now take 25% damage from damaging debuffs.
- Revengeance Mode changes:
  - Decreased enrage scale boost while on the surface, and surface enrage no longer triggers when in front of unsafe Crimstone walls.
  - Increased teleport distance and maximum velocity in phase 1.
  - Creepers now teleport with the Brain when not charging, and have a telegraph when they're about to charge.
  - Increased Creeper velocity, and velocity scales with how many Creepers are alive, but velocity is now less affected by enrage scale.
  - Decreased the maximum time before Creepers return to the Brain, and Creepers now fire blood shots when returning.
  - Increased knockback resistance, and now creates 4 additional clones in the cardinal directions in phase 2.
  - Now starts performing spinning lunges at 80% health instead of 60%, and fires a spread of blood shots during spinning lunges.
  - Now has a smaller spin radius, and waits longer before teleporting after a spinning lunge.
  - Now fires blood shots from 2 directions when below 60% health, and from 4 directions when below 40% health.
  - Now lunges faster, has a smaller delay between spinning lunges, has increased blood shot velocity, and can teleport to the cardinal directions when below 25% health.
  - Now lunges even faster and has an even smaller delay between spinning lunges when below 10% health.
  - Increased minimum backup distance before performing a spinning lunge from 25 tiles to 40.
- Now has more knockback resistance at the start of phase 2, creates 8 more faint illusions, has an even smaller delay before the spinning lunge, lunges even faster, shoots more blood shots in a larger spread, blood shots have increased velocity, Creepers charge even faster based on how many are alive, and Creepers no longer push away from each other in Death Mode.
- Now spawns 30 Creepers, it and Creepers gain a small boost to enrage scale, Creepers have immunity to knockback and less inertia, charge more often, and can charge for longer, and moves faster in phase 1 in Master Mode.
- Now makes Creeper charges predictive, has a faster phase 2 move speed and less inertia, spawns additional Creepers during phase 2, shoots more blood shots in a wider spread, charges at the player longer after spinning lunges, and spinning lunges are predictive in Revengeance Master Mode.

2.0.3.008: No longer deals contact damage in phase 1 in Revengeance Mode.

2.0.3.003: Nerfed speed in phase 1 in the Get fixed boi seed.

2.0.3.001: Buffed health from 1400 / 2380 / 2856 / 3033 / 3639 to 1500 / 2550 / 3060 / 3251 / 3901 .

2.0.1.002: No longer hides its minimap icon below 20% / 100% health.

1.5.1.003:
- Enters phases faster in Revengeance Mode.
- Charges faster in Death Mode.
- Creepers now spread out more in Death Mode.

1.5.1.001:
- Buffed health from 1000 / 1700 / 2720 to 1400 / 2380 / 2856 .
- Increased distance the boss teleports away from the player while enraged.
- In Revengeance Mode, Creepers no longer drop Crimtane Ores or Tissue Samples. The treasure bag now contains an additional 100-180 Crimtane Ores and 60-120 Tissue Samples.
- It and its Creepers are now vulnerable to cold, sickness, and heat debuffs.
- Now drops Brain of Confusion regardless of world difficulty.

1.5.0.003:
- Creepers now take 50% damage from Demon Scythe projectiles.
- Creepers can now drop Hearts when killed in Revengeance Mode.

1.5.0.002: Fixed Creepers incorrectly using enraged AI while not on Malice Mode.

1.5.0.001: Nerfed Boss Rush health from 1,000,000 / 1,700,000 / 2,720,000 to 100,000 / 170,000 / 272,000 .

1.4.5.004:
- No longer despawns outside of the Crimson but instead enrages in Revengeance Mode.
- Now less aggressive when fought in the Underground Crimson in Revengeance Mode.
- Now transitions to phase 4 at 55% health instead of 50% and phase 5 at 40% health instead of 30% .
- Nerfed Creeper's speed in Revengeance Mode.

1.4.5.003:
- Now gains increased movement velocity and decreased attack delay as its health decreases in Death Mode.
- Creepers now have increased velocity in Death Mode.

1.4.5.001: Implemented a boss kill time for the Creepers of 30 seconds.

1.4.3.001:
- Nerfed contact damage from 30 / 54 / 67 / 77 to 30 / 54 / 64 / 71 .
- Nerfed final phase contact damage from 80 / 92 to 76 / 84 .
- Nerfed Creeper's damage from 20 / 40 / 50 / 57 to 20 / 40 / 50 / 56 .
- Nerfed blood geyser damage from 60 / 69 to 60 / 67 .
- Death Mode changes:
  - Transitions into Phase 3, 4, and 5 immediately instead of below 90%, 70%, and 50% health.
  - Hitting the boss has the least effect on delaying teleportation immediately, instead of gradually having less effect as health lowers.
  - Has 99.1% knockback resistance immediately, instead of having 58.6% knockback resistance and gradually taking less knockback as health lowers.
  - Moves at the highest speed immediately, instead of gradually speeding up as health lowers.
  - Decreased Creeper speed.
  - Decreased teleport frequency while Creepers are alive.

1.4.2.106:
- Buffed Boss Rush health from 200,000 to 1,000,000.
- Buffed Creeper's Boss Rush health from 20,000 to 100,000.

1.4.2.105:
- Reworked Revengeance Mode AI:
  - Buffed health modifier from 1.4x / 1.9x to 1.6x / 2.1x .
  - Will never teleport on top of the player during phase 1.
  - Can now deal damage in phase 1 again.
  - If there are 5 or fewer Creepers alive, all Creepers become immune to knockback.
  - Creepers now take 60% damage from non-minion piercing projectiles.
  - Moves faster and teleports more frequently in phase 1 based on how many Creepers are alive.
  - Creepers now charge as a swarm more frequently if there are less alive.
  - Will not despawn if fought in the Crimson.
  - No longer has a map icon at low health.

1.4.2.104:
- Nerfed health modifier from 1.6x / 2.3x to 1.4x / 1.9x
- Nerfed Creepers' health modifier from 1.2x / 1.4x to 1.1x / 1.2x .
- Can no longer hit the player in phase 1.

1.4.2.103:
- Revengeance Mode changes:
  - Buffed health modifier from 1.4x / 1.9x to 1.6x / 2.3x .
  - Creepers now have a health modifier of 1.2x / 1.4x .
  - Creepers no longer respawn.
  - Can no longer hit the player in phase 1.

1.4.2.001:
- Nerfed Boss Rush health from 400,000 to 200,000.
- Nerfed Creeper's Boss Rush health from 40,000 to 20,000.

1.4.1.001:
- Buffed Boss Rush health from 200,000 to 400,000.
- Buffed Creeper's Boss Rush health from 20,000 to 40,000.
- Buffed Boss Rush damage modifier from 3x to 4x.
- No longer deals extra contact damage in Death Mode.
- Can no longer hit the player while teleporting.
- Decreased the speed at which Creepers spawn in phase 2.

1.4.0.001: Reduced Creeper respawn rates.

1.3.4.101:
- Buffed health modifier from 1.25x / 1.75x to 1.4x / 1.9x .
- It and its Creepers no longer have 10% damage reduction.

1.3.4.001:
- Nerfed health modifier from 1.8x / 3.4x to 1.25x / 1.75x .
- Increased rate at which Creepers spawn.
- Now has a maximum of 15 Creepers at a time instead of 10.

1.2.4.101: Buffed Death Mode health modifier from 2x to 3.4x .

1.2.4.002:
- Buffed health modifier from 1.5x to 1.8x .
- Lowered knockback resistance.

1.2.3.005: Now gains a 1.25x damage modifier in Death Mode, and Creepers now spawn every 3rd / 1st time the boss teleports in Revengeance and Death Mode.

1.2.3.004: Now gains extra knockback resistance in Death Mode.

1.2.3.002: Now gains a 2x health modifier in Death Mode.

1.2.0.004: Increased speed in Revengeance Mode.

1.2.0.002: Creeper now inflicts Marked for Death for 2 seconds in Revengeance Mode.

1.2.0.001:
- Now gains a 1.5x health modifier in Revengeance Mode.
- Now has a 2% chance to drop Laudanum or Stress Pills in Revengeance Mode.
- Now inflicts Horror for 3 seconds in Revengeance Mode.
- Creeper now inflicts Horror for 1 second in Revengeance Mode.

1.1.7.801: The status message "Bloody cysts are erupting from the crimson's flesh..." now appears when defeated.

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