These are the first bosses the player can encounter. Usually, defeating one of these bosses will give the player items and materials necessary to progress in the game, eventually leading to Hardmode.

King Slime is a giant blue slime with 2,000 health (2,800 in Expert Mode). It is summoned with a Slime Crown
, after killing 150 slimes during a Slime Rain, and can also rarely appear in the outer thirds of the map completely by itself. As with all monsters that can spawn naturally, the King Slime has a better chance of spawning while standing near a placed Water Candle or while under the effects of a Battle Potion. King Slime is a good challenge for a beginning player, and can be easily defeated by tactical use of terrain.

On the Desktop version, King Slime gains the ability to teleport to the player if they get out of its reach for too long.

King Slime does not provide access to game-advancing items upon defeat, but outside Expert Mode will drop one Gold Coin, one or two piece(s) of Ninja clothes, and one of several slime-related items.

In Expert Mode, the King Slime has much more health and can summon Spiked Slimes, that are similar to the Spiked Jungle Slime and Spiked Ice Slime.

The Eye of Cthulhu has a 1 in 3 chance of spawning at the beginning of each night once the player has 200 HP or more, 3 or more NPCs living in houses, and over 10 defense. It will continue to do so until defeated for the first time. It has 2,800 health in all (3,640 in Expert Mode). It can also be summoned using a Suspicious Looking Eye at night. This is generally the first boss a player must face. It travels through blocks, and spawns Servants of Cthulhu.

In Expert Mode, the Eye of Cthulhu will do a fast chain dash in its second phase, using the attack more often the lower health it has. This can lead to it dashing almost continually at very low health, making it especially difficult for players in the early game to finish it off.

The Eater of Worlds will appear after every third Shadow Orb is broken or after Worm Food is used. Shadow Orbs are found in the Corruption chasms, surrounded by Ebonstone, which requires a Pickaxe with 65% power or higher to mine, although explosives or Purification Powder can be used to bypass this. Once within range, Shadow Orbs can be destroyed with a Hammer. The Eater of Worlds can only be summoned in world containing Corruption, and can be summoned at any time of the day. If it manages to escape the Corruption, it will flee and disappear.

The Eater of Worlds can be a challenge even for intermediate players, as it is a large worm-type enemy that travels through tiles, and is made up of multiple sections that can each attack separately (with separate heads, no less) when they are cut off. To defeat this boss, every section must be brought down to less than two body parts to be killed (the smallest possible section is a head and a tail with no body pieces). Due to how helpful corrupted items are, this will probably be the second boss faced in worlds that have Corruption, rather than those who have Crimson.

Eater of Worlds is the only source of Shadow Scales in the game, and drops a large amount of Demonite Ore, which can also be sold for over 7Gold Coin, making this technically the best pre-hardmode boss for farming in the game.

In Expert Mode, the boss is able to shoot dark-green projectiles at you called Vile Spit, similar to those fired from Corruptors, another Corruption exclusive enemy.

The Brain of Cthulhu will appear after every third Crimson Heart is broken or after a Bloody Spine is used. Crimson Hearts are found in the Crimson's chasms, surrounded by Crimstone, which can be bypassed with the same methods Ebonstone can. However, some of the pockets containing these will generate open. Once within range, Crimson Hearts can be destroyed with a Hammer or any tile-breaking explosive. It can only be summoned in the Crimson and can be at any time of day.

Brain of Cthulhu has only 1,000 HP (1,700 in Expert Mode), making it have the lowest amount of HP out of any boss. The Brain of Cthulhu has two forms. In the first form, the brain cannot be harmed, and Creepers will float around it. After all of these are killed, the Brain of Cthulhu will go into its second form, where it will teleport more frantically and move a lot faster, so a ranged weapon may be needed. The Brain of Cthulhu's second attack form is ramming, alike the second form of Eye of Cthulhu. Unlike most other bosses, the Brain of Cthulhu is not immune to knockback.

In Expert Mode, the Brain of Cthulhu will have more health, and in its second phase, it will start creating illusions of itself to charge at the player. The lower the Brain of Cthulhu's HP gets, the illusions become much less obvious to the point where they will look exactly like the real Brain of Cthulhu.

The Brain of Cthulhu is the only source of Tissue Samples in the game (other than the creepers spawned while fighting it), and drops a large amount of Crimtane Ore, which are their equivalents to the corruption items.

Queen Bee is summoned by destroying the Queen Bee's larva, encased within the walls of Bee Hives located in the Underground Jungle. It can also be summoned by the use of an Abeemination anywhere in the Jungle biome. It is the only source of Bee Wax on the Pc only.png Desktop version and Mobile only.pngMobile versions, and cannot be obtained on the Console only.png Console versions . Queen Bee is immune to knockback.

Queen Bee alternates between charging at the player (gets faster as Queen takes damage in Expert Mode) and hovering above them whilst spawning bees.

Defeating Queen Bee doesn't really advance the game in a major sense, but it does provide some decent loot that can further help the player prepare for the boss battle against the Wall of Flesh, and also spawning in the Witch Doctor.

Skeletron is summoned by speaking to the Old Man NPC at the entrance of the Dungeon and activating his curse at night. Skeletron will alternate between attacking the player with its hands and performing a spinning attack. Its hands can be attacked and defeated to make the battle easier, although this is not required. If it has not been defeated before the night is over, Skeletron will attack and kill the player in one hit, despawning afterwards.

Defeating Skeletron will stop the Dungeon Guardians from spawning, allowing free access to the Dungeon. It can be summoned again by killing the Clothier with the Clothier Voodoo Doll equipped at night.

In Expert Mode, the fight is much harder. In the first phase, Skeletron's head is more resistant to damage until its hands are destroyed. Once they are destroyed, it will start shooting homing skulls at the player. Expert Mode Skeletron is much faster. Its hands inflict the Slow debuff, and its head inflicts Bleeding. If the player gets caught by its head-spin attack, Skeletron can "stun lock" them, and often kills very quickly unless the player can grapple out.

The Wall of Flesh is summoned by throwing a Guide Voodoo Doll into a pool of lava in the Underworld while the Guide is alive. It is known by most players as the hardest pre-Hardmode boss, at 8,000 health (11,200 in Expert Mode), and defeating it will irreversibly enable Hardmode in that given world. Its defeat will also allow the creation of the summoning items for various Hardmode bosses. It can drop several powerful items, one of them being the guaranteed drop Pwnhammer which can be used to break Demon Altars in order to spawn various game-advancing Hardmode Ores, including: Cobalt or Palladium, Mythril or Orichalcum, Adamantine or Titanium

Upon summoning the Wall of Flesh, the player will be afflicted with the Horrified debuff, which prevents fleeing from the battle. It will then sweep across the map, moving faster as its HP gets lower. It must be killed before it reaches the end of the map, otherwise it will despawn. Additionally, the Wall of Flesh's eyes fire lasers, its mouth burps Leeches that will chase the player, and it has small mouths attached to it called The Hungry, which will also move toward and damage the player.

In Expert Mode, The Hungry will rapidly respawn, and the Wall of Flesh will greatly increase its movement speed when it has 500 HP remaining, matching the full speed of Hermes Boots, so it is advised to wear the Lightning boots while fighting him in expert mode. The Hungry that quickly respawn will seemingly block the wall from attacks and can deal quite a bit of damage themselves. The faster the Wall of Flesh moves and the quicker the The Hungry respawn, the more the player will have to focus on dealing damage and moving across a decent terrain. This can prove to be difficult to some players.

Hardmode Bosses are significantly harder upgrades of and new additions to previous bosses. Defeating them is usually instrumental in advancing the game in some way. Each has its own particular way of being summoned, and warning messages appear whenever one is about to appear. Defeating a boss concludes with a congratulatory message and several items.

During Hardmode, each night has a one in two chance of spawning one of the three Mechanical Bosses that have not yet been defeated in the current world. This only happens after removing at least one Altar from the world, so it may be advisable to refrain from doing so if the player is not ready for a challenging fight.

The Twins are the Hardmode version of the Eye of Cthulhu. They spawn as two eyes, one with 20,000 HP (Retinazer) and one with 23,000 HP (Spazmatism). Unlike the Eye of Cthulhu, they do not immediately transform at half health - Retinazer transforms at 8,000 HP and Spazmatism transforms at 9,000 HP. These values are increased in Expert Mode. The Twins are summoned by using a Mechanical Eye at night. It is worth noting that The Twins will gain defense in their second forms, unlike the Eye of Cthulhu.

The two eyes have different fighting styles. Spazmatism focuses on slamming into the player and firing cursed flames. Once it reaches its second form, it will resemble a mechanical version of the Eye of Cthulhu's second form. It will deal a lot more damage, and the flames it shoots are more consistent like the Flamethrower instead of the Cursed Flames, but the flames will still inflict Cursed Inferno debuff on the player.

The other eye, Retinazer, focuses on shooting the player with Death Lasers like the Destroyer's Probes. Once it reaches its second form, it will replace its pupil with a laser cannon. During this form, it will shoot lasers extremely fast, sometimes having the same fire rate as a Megashark. The last Twin destroyed will drop all of the loot.

In Expert Mode Retinazer's HP is 30,000, while Spazmatism's HP is 34,500. Spazmatism's charging attack will also be similar to the Eye of Cthulhu's chain dash ability in its second form, and Retinazer will shoot lasers almost as rapid as the Wall of Flesh at 500 HP.

The Destroyer is the Hardmode version of the Eater of Worlds, with 80,000 HP (120,000 in Expert Mode). It is considered the easiest Hardmode boss by many players, despite having the second-highest health. Although it is similar to its pre-Hardmode counterpart, the Eater of Worlds, it has some key differences: it won't divide into smaller segments, will shoot lasers from its body if space is available, and will deploy Probes to attack.

The Destroyer is summoned by crafting and using a Mechanical Worm anywhere, but can only be spawned at night. The Destroyer will shoot Death Lasers, increasing in attack speed as it loses HP. Weapons that do damage to multiple segments like Flails, Water Bolt, and the Demon Scythe are recommended, because they will hit multiple sections of The Destroyer at once.

In Expert Mode, The Destroyer shoots rapidly at the player when they have less than half of their maximum HP. The head of The Destroyer can also deal damage as high a 280, crippling the player if they are hit head-on.

Skeletron Prime is a far more difficult Hardmode version of Skeletron, with the head alone having 28,000 HP (42,000 in Expert Mode). Instead of two hands, it has a vice, laser gun, saw, and cannon. With the head and all limbs combined, Skeletron Prime has 59,000 HP. However, like Skeletron, only the head has to be defeated. Skeletron Prime can be summoned as many times per world as needed, by crafting and using a Mechanical Skull, but he can only be summoned at night. It is worth noting that when his head spins, his defense increases, unlike Skeletron, whose defense is dropped to 0 when spinning.

He will drop Hallowed Bars and Souls of Fright, which are both used to craft many kinds of armor and tools. Like Skeletron, if he is not killed before the night ends, he will attack and kill the player in one hit, despawning afterwards.

In Expert Mode Skeletron Prime will have 42,000 health for the head, and doubled arm health. Skeletron Prime follows around the same guidelines as Skeletron; he is less resistant to damage after you kill his hands.

Plantera is summoned by destroying a Plantera's Bulb, which is found in the Underground Jungle after defeating all three Mechanical Bosses. It has 30,000 HP (42,000 in Expert Mode.) Also, if you exit the Jungle with Plantera following you, it will turn into Enraged Plantera, which makes Plantera orange and multiplies all of its stats by 3.

Plantera has two stages. In its first stage it clings to solid blocks using vine-like hooks and fires Seeds (and eventually Poison Seeds), which are much like Spiky Balls. In its second stage Plantera has increased speed and charges at the player. It will also release tendrils from its main body. In Expert Mode, the tendrils are attached to each hook instead (3 on each), adding approximately 9 tendrils.

Once Plantera is defeated, the Dungeon will automatically spawn more difficult Hardmode enemies, such as the Paladin, and more varieties of loot can be dropped.

The Golem is summoned by using a Lihzahrd Power Cell at the Lihzahrd Altar in the Jungle Temple. In order to access the Jungle Temple, Plantera must be defeated to obtain the Temple Key. It has a total of 39,000 HP (58,500 in Expert Mode).

Golem has two phases. During the first phase, its two fists and its head can be attacked. Like Skeletron, destroying the fists is not needed, but can be helpful. Once the head's health is depleted, it begins flying above the body while shooting fireballs and eye beams, leaving the body open to attack. The body will jump around and punch madly in this phase. Defeating the body will defeat
Golem.

In Expert mode, Golem gains a Regeneration factor if he is not damaged after a bit of time. This regeneration happens passively to Golem throughout the fight.

Duke Fishron is a fish-pig-dragon hybrid with 50,000 health and 50 defense. It is summoned when a Truffle Worm is used as bait with a higher-powered fishing rod in an Ocean biome.

In its first stage, Duke Fishron will attempt to ram the player 5 times before either firing explosive bubbles or summoning Sharknados. In its second stage, Duke Fishron gains glowing eyes and a boost to attack and defense (needs confirmation.) Although its ramming attacks remain the same, instead of shooting bubbles directly at the player, it flies quickly around in circles, sending bubbles everywhere. Instead of summoning Sharknados in this stage, Duke Fishron summons larger Cthulhunados. These remain in place until Duke Fishron is defeated. Duke Fishron is said to be the hardest boss in the game except for Pc only.png the Moon Lord, but the battle becomes much easier when the player has Wings equipped. Much of the difficulty of the Duke Fishron fight is from his speed, but it can be avoided by going around him in circles while using Wings.

In Expert Mode, when Duke Fishron gets to low enough health, he starts turning invisible and charging at the player with high speed.

The Lunatic Cultist is summoned by killing the four cultists, which spawn outside of the dungeon after Golem is defeated. When the Lunatic Cultist is defeated, the Lunar Events begin.

While the Lunatic Cultist has only one stage, its attacks become more powerful as it loses health. The Lunatic Cultist flies around randomly, cycling between shooting fireballs, creating a ball which shoots lighting in a circle, shooting a giant snowflake which shoots ice shards at the player, shooting shadowflames, and shooting five destructible projectiles twice in a row. The Lunatic Cultist will also create fake copies of itself, which will summon a Phantasm Dragon when damaged. If a Phantasm Dragon is still alive and the player damages these copies, it will summon an Ancient Vision instead. Waiting too long to attack the real Lunatic Cultist will also cause the Phantasm Dragon or Ancient Vision to be summoned. In Expert Mode, the Lunatic Cultist will spawn Ancient Doom along with its other attacks.

[/previewimg][/previewimg]The Moon Lord is the final boss of Terraria as of version 1.3.0.1, and drops a majority of the endgame items, such as the Meowmere. It also drops the end-game ore, Luminite, used to craft many endgame armor sets and tools. He is summoned by defeating all four of the Celestial Towers from the Lunar Events, or by using a Celestial Sigil. He has a combined health of 145,000 (217,500 in Expert Mode), the most health of any boss in the game.

The Moon Lord has two hands and a head which must be killed by attacking the eyes on them, and when killed will release invincible True Eyes of Cthulhu. When the three eyes are destroyed the Moon Lord's core opens up on his chest, which must then be destroyed to defeat the boss.

The Moon Lord's hands shoot two projectiles at once which home onto the player, and summon phantom versions of the True Eye of Cthulhu and throwing them at the player. The Moon Lord's top eye will occasionally fire a Phantasmal Deathray that will sweep across the entire screen. Being very deadly to players, it can be avoided by hiding under solid blocks or by trying to escape its wrath on a flying mount. When the True Eyes of Cthulhu are released, the places where they used to be will inflict minor contact damage. The True Eyes of Cthulhu will fire many of the same attacks as they did when they were still enclosed within the Moon Lord, but be a little less damaging. In Expert mode, the Moonlord's Phantasmal Death Ray attack deals a TON more damage, which is enough to kill a player in one shot.

Work on Progress guys :)