Guide:Brain of Cthulhu strategies

"A horrible chill goes down your spine..."

The Brain of Cthulhu is a Pre-Hardmode boss. It's The Crimson counterpart of Eater of Worlds.

Spawn Conditions
The Brain of Cthulhu can be spawned by fulfilling one of these conditions: It must then be defeated within the Crimson: getting out of it will make it retreat and despawn.
 * Smash three.
 * Use.

The Fight
Brain of Cthulhu has 2 phases, with the latter starting after all have been dealt with.

First Phase
The Brain cannot be attacked in this phase, only the Creepers can. The Brain will teleport to a spot in the arena, then slowly advance towards you. The Creepers will follow shortly after, and will clump up with the brain for a few seconds, before the Brain teleports again and the Creepers will follow. The idea is that the Brain will teleport behind you, which will make the Creepers to fly into you, causing damage. Jump out of the way, either by using your platforms or with an extra jump, then attack the Creepers. Use piercing weapons to speed up the process. When a Creeper dies it can drop either or.

Second Phase
When all of the Creepers are dead, the Brain will split, revealing a Heart with an Eye on the inside. The Brain teleports much more frequently, often at unexpected angles, and will try to ram into you. He only has 1000 health, so he can be killed fairly quickly. Keep using your platforms to jump out of the way. Use your strongest weapon to take down the Brain. If you have a weapon with high knockback, it will excel at dealing with the Brain, so much so that it's possible to stand in one location and attack it whenever it gets close.

Expert Mode
The Creepers are much more aggressive. They will actively try to fly into you, even ignoring the Brain if it means an opportunity to land an extra hit or two. They can also inflict a large variety of debuffs:
 * : reverses the movement buttons;
 * : saps 2 health per second;
 * : stops health renegeration;
 * : reduces vision;
 * : makes you unable to cast any Magic weapons;
 * : reduces your Defense by half;
 * : reduces Melee damage and Attack speed, Movement speed and Defense by 4.

During the Second Phase, the Brain will spawn clones of itself around the player. They serve as decoys, and while they cannot be attacked they can confuse the player. They start off as barely visible but as the Brain loses more health the clones will become more opaque. At low health the clones will be completely visible. The Brain will also become faster as it loses health. Life-draining debuffs such as On Fire and Frostburn, or a Hunter Potion will help distinguish them. Additionally, summoned Minions will always target the correct copy.

Terrain Preparation
Your arena will have to be built in The Crimson, because it can only be summoned there. Since the Brain of Cthulhu spawns as soon as you smash a third Crimson Heart, you're likely to be in a very enclosed area when the fight begins. This can lead to you to being swarmed by the Creepers and get overwhelmed. This can be avoided by preparing the chasm's main chamber as an arena beforehand, and choosing which Hearts to break first:
 * For the first two, pick the least convenient hearts (distant, above the main chamber, underwater, etc).
 * For the third, pick the closest to the main chamber, toss a Bomb or another explosive and quickly go to your arena while it falls.

If summoned with a Bloody Spine, then the arena can simply be made in the Surface, however do not make it very tall, as jumping too far above it will be considered exiting the Crimson, causing the Brain of Cthulhu to despawn.

Gearing up
It is recommended to have at least 200 Life and 100 Mana, which requires 5 and : if you've done some spelunking you're bound to have come across this many.

You're going to need at least Iron or Lead armor. Gold armor or Platinum armor is a great defensive choice with high defensive values for this point in the game.

For those playing during Halloween (or have planted some ), you can harvest for Pumpkin armor which has the same defense value as Iron's, but it trades off the +2 defense bonus with a helpful 10% damage bonus.

Weapons
For Melee users:
 * Blood Butcherer.png Any large sword, such as the Blood Butcherer will prove effective against the Creepers. The Falcon Blade is useful for the Brain of Cthulhu's second phase, as its rapid speed, somewhat high damage, and decent knockback will keep it at bay. The Katana, sold from the Travelling Merchant, is a fast sword with decent knockback and a high critical rate.
 * The Rotted Fork.png A Spear is a great weapon against the Brain of Cthulhu, especially during the second stage. Suggested options are the Trident and The Rotted Fork.
 * A Flail of some kind is beneficial for taking out the Creepers; the easiest to obtain would be the, but this will require you to make another world with The Corruption in it, as it cannot be acquired in a Crimson world. You could instead try to obtain the , rarely dropped by , but unlike the previously mentioned flail, it cannot pierce.

For Ranged users:
 * is the most powerful bow at this stage. You can combine it with, which greatly help to kill the swarm of Creepers. However, you can also use the as a cheaper alternative; the  debuff will be helpful during the second stage.
 * As can be obtained very easily (as it's a guaranteed first-time loot from the Hearts), it's a good weapon to use against the Brain. The  that spawn with it should be sufficient, but you can craft (or buy), which deal slightly more damage.

For Magic users:
 * The and  are good choices, and are obtained fairly easily. They greatly benefit from fighting in an enclosed area.
 * The is easy to make, but it's time-consuming. But you'll find its piercing ability excel at dealing with the Creepers.
 * If you're willing to make a quick detour to a Corruption world, the works fantastically against the Creepers and is a great weapon in general.
 * If you already farmed a Meteorite crash site for Meteorite, you can use the excellent with Meteor armor: its piercing ability will clear out the Creepers fairly easily, and it will cost no mana thanks to the set bonus of Meteor armor.

For Throwing users:
 * and, with their Penetration, can be helpful for killing Creepers. Poisoned Knifes can be crafted using Vicious Powder and Throwing Knives and deal a little extra damage.
 * If you are willing to risk, are great choices for dealing with the Creepers, but you have to watch out for the blast radius, as you will take damage from it.
 * , while expensive to make (as aren't common), is a superb weapon. The splash damage and the fire that hits multiple times can keep the Brain away in its second stage.

For Summoners:

At this stage of the game, it's better to use any of the already mentioned Gear tips, as there isn't much to use, unless you want to kill Queen Bee first, which is not recommended at this time.

Potions

 * The Ironskin Potion, the Swiftness Potion and the Regeneration Potion will do you well.
 * You should try to get the Well Fed Buff in some way; you can get this from Cooked Fish or Pumpkin Pie.

Accessories

 * The Cloud in a Bottle will give you a double-jump ability which will greatly help with evasion. Look out for the improved versions, such as the Tsunami in a Bottle, the Blizzard in a Bottle or the Sandstorm in a Bottle.
 * The Hermes Boots will increase your speed and aid greatly in evasion. You can upgrade them to the Spectre Boots for the added bonus of a few seconds of flight, but this requires the Goblin Tinkerer, which the player may not have yet.
 * The Band of Regeneration is a decent accessory which will slowly regenerate your life; it equates to one heart restored every 40 seconds. Not terribly useful but it's suggested if you have a slot you need to fill.
 * The Anklet of the Wind gives a basic 10% speed boost, which will help out with evasion. You can replace it with the Aglet which is much easier to find but only offers a 5% speed boost.
 * The Frog Leg will give you improved jumping abilities, including increased height and automatic jumping but it can only be found by fishing, with an incredibly rare 1:500 chance to get it.
 * If one is playing in Expert mode, the Shield of Cthulhu is a great choice for quick evasion, and extra damage in the Brain's second phase.

Water Bolt box Method
If you can get a Water Bolt from the Dungeon, it allows for a fairly good advanced strategy: Build a closed box (about 15x15), making sure you can get into it quickly for the fight. Once the Brain appears, spam the Water Bolt to fill the box with bouncing bolts, which will rapidly kill Creepers passing through (quickly triggering the Brain's second form), then keep the Brain mostly away from you by knocking it back it every time it comes through the box. Make sure you have enough Mana or a Mana Flower!