The Zenith sword is by far the strongest sword in Terraria, and few other weapons rival its power.
Zenith was added to the game via the Journey’s End update. How it attacks is too awesome to describe with mere words. Just look at the clip below.
— Calixte Viollet (@calixte_viollet) May 16, 2020
To craft the Zenith, you need to take nine specific weapons to either a Mythril or Orichalcum Anvil, each one symbolizing a step in the progression of the game: Copper Shortsword, Starfury, Enchanted Sword, Terra Blade, Seedler, The Horseman’s Blade, Influx Waver, Star Wrath and Meowmere.
Here’s how to get each of the swords needed to craft the Terraria Zenith:
All newly created players will have a Copper Shortsword in their inventory, according to the Terraria Wiki. If you got rid of your sword, then just take seven Copper Bar to an Iron or Lead Anvil.
The Starfury can be found on the Floating Island Biome. You’ll be able to find one easily once you get the Rocket Boots and Grappling Hook from the Goblin Tinkerer (though be sure to use an item that negates fall damage). Once you find a Floating Island, you’ll be able to find the Starfury in a Skyware Chest on the island, though you may find a Shiny Red Balloon, Lucky Horseshoe or Sky Mill instead. If the Floating Island has a lake, you can try fishing for a Sky Crate which has a 1 in 6 chance of giving you either a Starfury, a Lucky Horseshoe or a Shiny Red Balloon according to the wiki.
If you don’t find a Starfury on any of the Floating Islands, then create a new world and look for the Floating Islands there.
Not to be confused with the enemy of the same name, the Enchanted Sword can be found in two different ways. The first way is by breaking Background Sword sprites found in the world. You won’t get anything if the sprite shows a brown sword – those are fake swords. You need to break the sprites with a blue sword. See the picture in the wiki. The second way is by finding an Enchanted Sword Shrine minibiome somewhere usually underground. The minibiome will have a sword sprite. You have a 2/3 chance of getting a fake sword sprite and 1/3 chance of getting a real sword sprite. Keep in mind that when breaking the real sword sprite, you have a 1/10 chance of getting an Arkhalis instead.
To craft the Terra Blade, you need to craft the True Excalibur and True Night’s Edge and then craft them together at a Mythril/Orichalcum Anvil.
The crafting tree for the Terra Blade can get a bit crazy, so check the wiki for a comprehensive picture of the process.
To get the True Night’s Edge, you first need a Night’s Edge, which is crafted at a Demon/Crimson Altar with the Blade of Grass, Muramasa, Fiery Greatsword and Light’s Bane/Blood Butcher. Craft the Blade of Grass by taking 12 Jungle Spores and 12 Stingers from the Jungle Biome to an Iron/Lead Anvil. The Muramasa is found in the Dungeon Biome randomly in locked Gold Chests, which can be opened getting a Gold Key which is a guaranteed drop from a Dungeon Slime. To get the Fiery Greatsword, mine Obsidian (combine water with lava) and Hellstone in the Underworld, make 20 Hellstone Bar at Hellforges in the Ruined Houses of the Underworld and then take the 20 Hellstone Bar to an Iron/Lead Anvil. Get Demonite Ore in a world with Corruption to craft 10 Demonite Bar at a Furnace and then take them to an Anvil to get a Light’s Bane. Do the same with Crimtane Ore in a world with Crimson to get the Blood Butcherer. You only need either the Light’s Bane or the Blood Butcherer.
To get the True Excalibur, you first need the Excalibur which is crafted from 12 Hallowed Bar at a Mythril/Orichalcum Anvil. Hallowed Bars are dropped from the three mechanical bosses, The Destroyer, The Twins and Skeletron Prime.
To turn the Excalibur and Night’s Edge into their true forms, you need to craft them each with a Broken Hero Sword at a Mythril/Orichalcum Anvil. The Broken Hero Sword has a 25% chance of dropping from Mothron, which spawns during a Solar Eclipse but only after you have beaten all three mechanical bosses. You need to get two of them from this enemy, so you need to beat it at least twice.
The Seedler has a 14% chance of dropping from Plantera, according to the wiki. Plantera is summoned by breaking a pink bulb that spawns in the Jungle Biome after defeating all three mechanical bosses.
The Horseman’s Blade
The Pumpkin Moon event has you fighting waves of enemies until dawn. It can be triggered anytime at night with the Pumpkin Moon Medallion, which is crafted at a Mythril/Orichalcum Anvil from 30 Pumpkin, 5 Ectoplasm (from Dungeon Spirits in the Dungeon post-Plantera) and 10 Hallowed Bar. According to the wiki, the Pumpking starts spawning on the seventh wave of the event.
To trigger a Martian Madness event, you need to have defeated the Golem. The Golem can be found in the Jungle Temple, which opens after beating Plantera. The Golem is summoned by activating the altar at the chamber at the end of the temple while you have a Lihzahrd Power Cell from one of the chests in the temple.
Once you beat the Golem, a Martian Probe enemy will start spawning in the the two outer lateral thirds of the map and especially in space according to the wiki. If the probe sees you or you attack it, it will turn red and attempt to flee. Letting it go will trigger the invasion.
Star Wrath & Meowmere
Star Wrath and Meowmere both drop from the Moon Lord.
To fight the Moon Lord, you first need to defeat the Cultists that spawn outside the entrance to the Dungeon after the Golem is defeated. The Lunatic Cultist will then spawn. Defeat that boss to trigger the Lunar Events. Four Celestial Pillars will spawn throughout the world. Before you can destroy each one, you need to defeat at least 100 of the unique enemies that spawn while the pillar is active. Once you destroy all four pillars, the Moon Lord will spawn in a minute. You can also summon the Moon Lord by using the Celestial Sigil item, which is crafted at the Ancient Manipulator dropped by the Lunatic Cultist. You need 20 each of the unique materials that drop from the Celestial Pillars.