Bosses

Bosses are large, aggressive, resilient enemies that offer a substantial challenge to players. There are currently 3 Bosses, each with its own particular way of being summoned. Warning messages appear whenever a Boss is about to begin attacking a player. Defeating a Boss concludes with a congratulatory message and several items.

Eye of Cthulhu
The Eye of Cthulhu is summoned with the Suspicious Looking Eye. It also has a chance of appearing on a random night until it has been defeated once; if it is not defeated on its first random spawning, it will have a 1 in 3 chance of spawning each night until it is defeated. It can also be summoned multiple times using the Suspicious Looking Eye, even after being defeated.

Since this Boss can spawn randomly without deliberate action by the player, it is often the first Boss the player must face. It is also considered the easiest Boss to defeat, though it is still a significant challenge, especially to newer players.

Eater of Worlds
The Eater of Worlds is summoned with the Worm Food, or can appear after smashing three Shadow Orbs. This Boss can also be summoned multiple times even after being defeated. The Eater of Worlds can be a tough challenge even for intermediate players, as it is a large Worm enemy that travels through walls, and is made up of multiple sections that each continue attacking when detached from each other.

The Eater of Worlds is the only source of Shadow Scale, and drops a large amount of Demonite Ore.

Skeletron
Skeletron is summoned by speaking to the Old Man at the entrance of the Dungeon at night. This is the only way to summon Skeletron, and once defeated he can not be summoned again. Skeletron is considered the most challenging enemy, as he deals the most damage and has the highest amount of Health. Defeating Skeletron allows you to access the Dungeon without being killed by Dungeon Guardians. The Dungeon contains many unique items, as well as hazards.

The Twins
The Hard version of the Eye of Cthulu

The Destroyer
The Hard Version of the Eater of Worlds

Skeletron Prime
Skeleton Prime is a far more difficult version of Skeletron requiring more squill and better weapons.