In Terraria, there are multiple bosses for you to take on. Each of these bosses has a specific summon requirement that you will need to meet, either solo or with a group of friends.
Summoning all bosses in Terraria
Terraria has three kinds of bosses: pre-hardmode, hardmode, and event bosses.
You must use Worm Food or break three Shadow Orbs. You can create Worm Food by finding 30 Vile Powder and 15 Rotten Chunks and bringing them to a Demon or Crimson Altar. Otherwise, it will have no effect and will not summon the boss.
You must obtain Worm Food or break three Shadow Orbs. You can find Worm Food by finding 30 Vile Powder and 15 Rotten Chunks in a Demon or Crimson Altar. After crafting it, you must proceed to the Corruption portion of the game and consume it. Otherwise, it will have no effect and will not summon the boss.
The only way to invoke the Eye of Cthulhu is to use the Suspicious Looking Eye. The item requires six lenses to be created at a Demon or Crismon Alter, or you may loot it by looking inside gold and frozen chests in the Cavern and Dungeon or ivy chests in the Jungle.
The King of Slime can only be summoned by using the Slime Crown. The only way to make it is by using 20 Gel with a Gold Crown or a Platinum Crown and then placing it in a Demon or Crimson Altar.
The first is to create the Abbemination and use it in the Jungle biome. After that, you need to have a bottled jar of honey, five honey blocks, and a stinger on you. Or, you may find the Queen Bees Larva inside a Bee Hive in the Jungle biome.
Skeletron is the way you get access to all Dungeons in the game, therefore it's crucial to have a chance to summon it at this time. Talking to him at this hour activates a curse and summons the boss to your location. After defeating Skeletron once, you can summon it again by killing the Clothier, an NPC who sells vanity items to you, and it's nighttime.
The Guide Voodoo Doll, the first NPC near you at the start of the game, must be alive at the time you throw it into the burning pit. You may remove Voodoo Demons in The Underworld to find the Guide Voodoo Doll.
Once you have discovered a Truffle Worm in the Glowing Mushroom biome, use it as bait on your fishing pole in the Ocean biome.
To summon the Empress of Light, you must defeat Plantera before it spawns. After that, you can find a prismatic Lacewing in the Surface Hallow starting from dusk until midnight, and you must capture it with a bug net. You can then release the creature at any time in any biome and kill it to summon the Empress of Light.
The giant Golem can only be summoned using a Lihzahrd Power Cell located in the Jungle biome. The power cells have a chance to deduce from the lihzahrd and flying snake creatures found inside the temples, or you can find one inside the lihzahrd chest.
You must first defeat the Golem and then find the four cultists standing at the entrance to the Mysterious Tablet at the Dungeon entrance. The Lunatic Cultist will arrive when you kill these four cultists.
The Moon Lord may be summoned in two ways. The first is to destroy all four Celestial Pillars that appear in the Lunar Event, which starts when you defeat the Lunatic Cultist. They appear in four different locations throughout the map. The second method is by crafting a Celestial Sigil, which you can do once you have 20 solar fragments, 20 vortex fragments, 20 stardust fragments, and an ancient Manipulator crafting station.
After defeating The Destroyer, The Twins, and Skeletron Prime, you may discover Planteras Bulbs in the Underground Jungle biome, and see the message, The jungle becomes agitated, on screen.
To summon Queen Slime, you need to find Gelatin Crystals in the Underground Hallow. These crystals are located in Pearlstone or Pink Ice Blocks. You may use the Gelatin Crystal to summon the Queen whenever you want.
Skeletron Prime appears only after consuming a Mechanical Skull at night. It does not work during the day. This item may only be created using 30 bone, five iron bars, three souls of light, and three souls of night.
You can only summon The Destroyer by consuming a Mechanical Worm during its night, much like you can with Skeletron Prime. You must craft this item at a Mythril or Orichalcum anvil using six rotten chunks, any iron bars, and six souls of night, or using six vertebra, five iron bars, and six souls of night.
The Twins will only appear in your game when you use the Mechanical Eye during the night. This item can be created using three lenses, five iron bars, and six souls of light.
Betsy appears during the last stage of the Old Ones Army event during a tier 3 event. You must buy an Eternia crystal from the Tavernkeep for 25 silver coins before defeating the Mechanical Bosses (Skeletron Prime, The Destroyer, and the Twins), one gold coin after defeating the Golem.
When battling the Old Ones Army in the tier 1 event, the Dark Mage appears as the final boss. As stated above, you must use the Eternia Crystal to summon the Old Ones Army.
During the Frost Moon event, the Everscream appears. At night, you must use the Naughty Present. You may craft the Naughty Present at a Mythril or Orichalcum anvil using 20 silk, five ectoplasm, and five souls of fear.
During the Pirate Invasion, the Flying Dutchman appears. You can start the Pirate Invasion by using the Pirate Map, which has a chance to drop from enemies near the Ocean Biome in hard mode. Alternatively, the Pirate Invasion has a chance to happen if no other events are happening, the Wall of Flesh has been defeated, at least one of the Altars has been destroyed, and the player has at least 200 maximum health.
The Ice Queen is the last boss to appear during the Frost Moon event, which you can begin by consuming the Naughty Present at night.
During the Martian Madness event, the Martian Saucer appears. After defeating the Golem, you must discover a Martian Probe. These probes can occur anywhere on the map, and if they escape, the event begins.
The Mourning Wood is a mini-bosse that you may defeat in the Pumpkin Moon event after defeating Plantera and using the Pumpkin Moon Medallion at night. It will require 30 pumpkins, five ectoplasm, and 10 hallowed bars to craft it and to devour it in a Mythril or Orichalcum anvil.
During the Old Ones Army tier 2, the Ogre is one of the bosses you may encounter.
During the Pumpkin Moon event, the Pumpking will serve as the second or final boss.
Santa-NK1 is a mini-boss that you can fight during the Frost Moon event if you use the Naughty Present at night.
After defeating the Lunatic Cultist during the Lunar Events, the Stardust, Solar, Vortex, and Nebula pillars appear on the map. Each pillar can be seen on different sections of the map with unique planets in the background.