Eye of Cthulhu

"You feel an evil presence watching you..."

The Eye of Cthulhu is a pre-Hardmode boss. This is one of the first bosses a player encounters, as it spawns automatically when a relatively early level of game advancement is achieved. It can also be summoned manually with the Suspicious Looking Eye (see Spawn below). It can be considered the second easiest boss in the game (the first being King Slime), though can still present a challenge to newer players.

While the Eye of Cthulhu is alive, music Boss 1 will play.

Spawn
The Eye of Cthulhu can be summoned manually using a Suspicious Looking Eye at Night (beginning at 7:30pm in-game time).

It also has a 1/3 chance of spawning automatically each night, if the following conditions apply:


 * The Eye of Cthulhu has not yet been defeated in the current world.
 * At least one player in the world has at least 200 life and more than 10 defense.
 * At least three Town NPCs are acquired.

When spawning automatically, its approach is signaled with the status message: "You feel an evil presence watching you..." 81 seconds after this message's appearance (about 8:51pm in-game time), the Eye of Cthulhu will appear and begin attacking the player.

If the Eye of Cthulhu is not defeated by Dawn (4:30am), or if all players die or run away while fighting it, it despawns.

Behavior
The Eye of Cthulhu has two phases, and is able to fly through blocks in both of them. During the first, it attempts to float directly above the player, while spawning 3-4, which drop Hearts and Stars on death. After spawning a round of those, it rams at the player 3 times in succession, before repeating the cycle.

When the Eye of Cthulhu falls below half health (65% in expert mode), it transforms into its second form (which sheds its pupil into a mouth), which rams the player more aggressively 3 times, then hangs in the air for a period. It no longer spawns Servants, and has no defense, but now has increased attack.

In, the boss spawns more Servants than normal, as well as 4-5 Servants upon transforming. At 1/25 health, it will gain an additional powerful rapid chain dash attack. These become faster as the Eye of Cthulhu's life is lowered, and it can dash nearly continuously when close to death.

Likewise, if morning comes before it is killed, it will fly off the screen and despawn.

Tips

 * The Eye of Cthulhu drops either Demonite or Crimtane Ore. While the corresponding set of armor and a number of tools additionally require Shadow Scales or Tissue Samples respectively – which the Eye does not drop –, sword, bow, axe, yoyo, and fishing rod can be crafted with only the bars.
 * Due to the ease of crafting its summoning item and relatively low difficulty, farming the Eye of Cthulhu is one of the more effective ways of making money prior to Hardmode. It drops (normal) /  (Expert) up front, plus ores which can be sold as bars for twice (Demonite) or thrice (Crimtane) that amount.
 * The Eye of Cthulhu will only spawn randomly if a player has 10 or more defense. Taking defense-boosting equipment off before sundown can prevent it from spawning randomly.
 * The boss looks at the player it will follow, which can be helpful information in Multiplayer.
 * When it is spinning, it is most vulnerable because it does neither move nor attack.
 * Because there are no location-based requirements for summoning, slaying multiple Eye of Cthulhu in an area can be an effective setup for harder boss fights as the hearts can be picked up mid-fight as needed.
 * Despite the fact that the Flare Gun does 3 damage on contact with an enemy, this weapon can be very effective against the Eye of Cthulhu. A Flare inflicts the debuff On Fire! on contact with an enemy. On a Zombie this effect does 1 damage at the time, but on the Eye of Cthulhu this damage is 17 lasting 5 (66%) to 10 (33%) seconds dealing in total around 238 – 425 damage per flare.
 * In Singleplayer, the player can repeatedly pause the game using Autopause in order to properly aim at the Eye of Cthulhu during its dash attacks.

Trivia

 * Cthulhu is an entity from the works of writer H.P. Lovecraft, first appearing in his short story, The Call of Cthulhu. Cthulhu is described as a slumbering cousin to the old ones who will destroy all living things should he ever awaken.
 * Cthulhu itself does not appear in any version of Terraria. However, Moon Lord, the final boss of the, is somewhat like a brother to Cthulhu, according to Cenx.
 * The Merchant NPC will mention sensing something evil watching them once you meet the requirements to battle the Eye of Cthulhu.
 * It is not required to defeat the Eye of Cthulhu as it has no unique drops required for game progression. It will however continue spawning until beaten at least once.
 * It is possible to outclass the Eye of Cthulhu with late-game weapons or Heart Arrows, causing it to never transform into its second form. However, its remains will be unaffected once killed.
 * The trophy dropped by the Eye of Cthulhu seems to be a tooth, which is only physically seen in its second form.
 * The Eye of Cthulhu seems to have Central Heterochromia.
 * It is one of the first bosses of Terraria's first release.
 * The Merchant’s quote is a reference to Cthulhu being ‘unpronounceable’

History
Auge von Cthulhu Œil de Cthulhu Eye of Cthulhu Eye of Cthulhu Глаз Ктулху 克苏鲁之眼