Eye of Cthulhu

. The Eye of Cthulhu is a Boss monster that the player can fight. It can be summoned by using a Suspicious Looking Eye, which is crafted at a Demon Altar or found in a Chest. In order to summon the boss, it must be night; otherwise, nothing will happen. If the Eye is not defeated by dawn, it flies away and despawns.

It is also possible for it to spawn naturally. This happens when the player has at least ten hearts (200 life), more than 10 defense, has at least 3 NPCs, and hasn't defeated the Eye of Cthulhu before. As long as these conditions are fulfilled, there will be a 1 in 3 chance each night of receiving the message, "You feel an evil presence watching you." Soon afterward, the Eye of Cthulhu will appear.

Farming the Eye of Cthulhu is one of the most effective ways of making money prior to Hardmode, second only to the Eater of Worlds in one-time drop value. Its coin drop, combined with selling its item drops, will yield an average of 7 in total each time. Mid- to end-game armor and weapons make the fight very easy.

Behavior
The Eye of Cthulhu looks like an enormous Demon Eye, but it behaves quite differently. During the first stage of the fight, it alternates between hovering overhead and trying to ram the player. When hovering, the Eye will spawn Servants of Cthulhu. If the player remains still at this time, the Eye will position itself directly overhead. When ramming, it will charge at the player 3 times, often going through walls and diving underground.

After the Eye loses more than 1400 health, it will transform into its second stage. In this form, the Eye of Cthulhu is faster and deals more damage, but has no defense and no longer spawns Servants of Cthulhu. It will charge at the player 3 times, then pause for a moment and hover overhead before repeating.

While the Eye of Cthulhu drops Demonite Ore, it will not drop Shadow Scales. Some Demonite items (such as Shadow armor and the Nightmare Pickaxe) cannot be crafted without Shadow Scales, which are dropped by the Eater of Worlds.

Trivia

 * Cthulhu is an entity from works by the writer H.P. Lovecraft, first appearing in his short story The Call of Cthulhu. Cthulhu is described as a slumbering Elder God who will destroy all living things should he ever awaken.
 * In Team Fortress 2 there's a boss that is similar.

History
Œil de Cthulhu Eye of Cthulhu Eye of Cthulhu Глаз Ктулху