Eye of Cthulhu

The Eye of Cthulhu is a pre-Hardmode boss. It 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 at night (see Spawn below). It can be considered the second easiest boss in the game, the first being King Slime.

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 maximum health and more than 10 defense.
 * At least three Town NPCs have been acquired.

If spawning this way, its arrival is announced by the status message ""

If the Eye of Cthulhu is not defeated by dawn (4:30AM), if all players die, or if the Eye of Cthulhu goes too far off-screen, it will despawn.

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. A servant is spawned with the. Afterward, it charges at the player 3 times in succession, before repeating the cycle.

When the Eye of Cthulhu falls below 50% health (0) in normal mode, or health in Expert mode, it transforms into its second form (shedding its iris 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. It now lets out a every time it charges.

In, the boss spawns more Servants than normal, as well as 4-5 Servants upon transforming. In the second phase, it will gain an additional powerful rapid chain dash attack, it lets out a everytime it dashes. These dashes become faster as the Eye of Cthulhu's life decreases, and it can dash nearly continuously when close to death.

In Master mode, all mobs and bosses have an increased health depending on the health of the expert mode variant. The Eye of Cthulhu in master mode has HP, an additional  HP over expert mode. It will enter second form when its health falls below HP. Other expert mode elements apply.

Likewise, if it is not killed before dawn, 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 pole 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 dusk can prevent it from spawning randomly.
 * The boss looks at the player it will follow, which can be helpful information in multiplayer.
 * The Eye is most vulnerable during its transformation, because it neither moves nor attacks. However, there is only a brief window of opportunity for this.
 * Because there are no location-based requirements for summoning, defeating multiple Eyes of Cthulhu in an area can be an effective setup for harder boss fights as the dropped Hearts can be picked up mid-fight as needed, though killing Eye of Cthulhu for that purpose must be balanced with the time it takes away from killing a night-only boss.
 * Killing it on a Corruption world is slightly more profitable than doing so in another with Crimson, as it will drop additional Unholy Arrows.
 * 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.
 * Building some rows of Platforms in the air can be helpful to dodge its attacks, especially if the player is using Hermes Boots, allowing them to out-run the Eye.
 * The Slimy Saddle is recommended for the first phase, as you can bounce on it into the sky as it follows you, dealing lots of damage. It is recommended have some means of negating fall damage while doing this.

Trivia

 * Assuming that the player is at 5′ 9½″ (1.75 m) in terms of height, The Eye of Cthulhu's first form would be about 13′ (4 m) tall and wide. The teeth would be 2.6′ (0.8 m) long.
 * The Eye of Cthulhu, among several other bosses, is based on Cthulhu, a creature first imagined by in his short story .
 * The existence of the, an entity spawned by the Moon Lord (who bears resemblance to Cthulhu), may imply that the Eye of Cthulhu is not Cthulhu's actual, true eye.
 * The Merchant NPC will mention sensing an evil presence watching him once the requirements to battle the Eye of Cthulhu are met.
 * Although irrelevant to game progression, the Eye of Cthulhu will keep spawning naturally until defeated at least once.
 * It is possible to defeat the Eye of Cthulhu without it ever transforming into its second form, e.g. with late-game weapons or . However, its remains will be unaffected once killed.
 * The Eye of Cthulhu Trophy seems to consist of a tooth, which is only physically seen in its second form.
 * The Eye of Cthulhu seems to have central, an eye condition where there are two colors in the same iris.
 * The Eye of Cthulhu was one of the first bosses added, debuting in update 1.0
 * The Eye of Cthulhu is sometimes abbreviated as "EoC".