Eye of Cthulhu

The Eye of Cthulhu is a Boss monster that the player can fight. It can be summoned by creating a Suspicious Looking Eye at a Demon Altar. In order to summon the boss, it has to be Night time; otherwise, the player will take thousands of points in damage. The boss has been described as the easiest by the game's developers.

Strategy
The Eye of Cthulhu acts like a larger Demon Eye, flying around and trying to ram the player, often going through walls and underground. Because of its large size, a bow or Shuriken are recommended to be brought to the fight, as the player can jump and dodge while constantly hitting the Eye.

When the Eye starts to spawn Servants of Cthulhu, stand still and it will position itself directly above you and look down. You can use this to your advantage by hitting it rapidly with a ranged attack (preferably one that passes through multiple enemies like Shuriken or the Ball 'O Hurt). Not only will this damage the Eye of Cthulhu, but the Servants of Cthulhu that it spawns will be killed instantly.

After the Eye loses half of its health, it will transform, losing its pupil, which is replaced by a large mouth. Its attacks become more powerful and it becomes faster. After it is defeated, it will gib just like a regular enemy and drop items, including Demonite Ore.