First of all you need to know which swords you need to craft this weapon because these are the fundamentals for this sword.

You need every sword from the following list (also in Picture 1):

• Terra Blade
  
• Meowmere
  
• Star Wrath
  
• Influx Waver
  
• The Horseman's Blade
  
• Seedler
  
• Starfury
  
• Bee Keeper
  
• Enchanted Sword
  
• Copper Shortsword

Picture 1: Overview of the swords


Also, the crafting / how to obtain these swords is a pain in the a**. Here is a short overview of every step you need to do, but we'll cover everything later:

Picture 2: Overview of the crafting

Some information you might need to know / be aware of:
You need 6 different crafting / smelting stations, a ton of luck and a lot of patience. The Zenith also is a Post-Moonlord weapon. In other words: you need to kill the endboss without it (Probably even 5 times or more). Its best modifier is legendary (without this modifier, it does 190 melee damage).
FunFact: Originally it was a completely different one, which then got redesigned. You can't obtain the 'original Zenith' anymore in Terraria.

For the start you should prepare an iron or lead anvil and a furnace. You should also expand your knowledge when it comes to pickaxes because you need to upgrade them a lot in this process. Also, at some point, you need to switch to drills to get certain types of ore.
Here is a short list of the pickaxes and their power:
Picture 3: Pickaxes and their power

And here is a short list of the drills and their power:
Picture 4: Drills and their power

Now in the next sections I will cover every single sword. From how find the materials to how to craft it. (I will go from left to right like in Picture 2)

These swords can be obtained before defeating the Wall Of Flesh

This is the simplest sword you need to craft. I will not cover the exact way to craft the stations you need to use as it is fundamental for any weapon to have those.

To craft the Copper Shortsword, you need the following ingredients / buildings:

Buildings:

• Iron/Lead Anvil
  
• Furnace

Ingredients:

• 15 Copper Ore

You then smelt the Copper Ore in the furnace to get 5 Copper Bars, which can be used on the anvil to craft the Copper Shortsword.
That's it. But don't worry, it won't stay that relaxing...

This weapon is also one you can't craft. But this time you have to find it, similar to the Enchanted Sword. You have to either build yourself up in the Sky to find Floating Islands (Picture 8) or craft / find wings to fly up.

Picture 8: Floating Island with Starfury Chest

On these floating Islands there will be Chests (Picture 9) or Crates (Picture 10) in which you will be finding the Starfury.




Picture 9: Sky Chests






Picture 10: Sky/Azure Crates

The Enchanted Sword is a bit more challenging, because you can't craft this one. You have to find it underground. Right under the surface, somewhere on the map, there should be a shaft which leads to a shrine (Picture 6). When you are in luck, you get a "real shrine" (on the right in Picture 5). When this isn't the case, you will get a fake one (on the left in Picture 5). This will cause the chances of the Enchanted Sword beeing dropped to 0%.




Picture 5: Junk and Enchanted Sword

Picture 6: Enchanted Sword Shrine

The last thing to do is to break the shrine with a hammer to obtain the Enchanted Sword

The Bee Keeper is also a sword you can't craft. It is dropped by the Queen Bee by a chance of 33%. In other words: you could have to defeat the Queen Bee more than one time.

The Queen Bee is a Boss Monster which can be found in the Underground Jungle Biome. You have to look for a giant bee hive (Picture 7) and destroy the Larva to summon it.








Picture 7: Bee Hive with Larva (on the right)

Guide on how to defeat the Queen Bee by Insanemind:
https://www.youtube.com/watch?v=QCnEFt3g_38

You can only obtain these swords when you defeated the Wall Of Flesh and all Mechanical Bosses (Skeletron Prime, The Twins, The Destroyer)

Guides on how to defeat the Wall of Flesh and Mechanical Bosses by WaffleTime:

Wall of Flesh:
https://www.youtube.com/watch?v=69DdffmXKY4&list=PLmR34ZNlknNY5ns-B9UAGXllF2UPGh3M1
Skeletron Prime:
https://www.youtube.com/watch?v=vW_qY67Tmr8&list=PLmR34ZNlknNY5ns-B9UAGXllF2UPGh3M1&index=4
The Twins:
https://www.youtube.com/watch?v=UB7c7f707Vw&list=PLmR34ZNlknNY5ns-B9UAGXllF2UPGh3M1&index=3
The Destroyer:
https://www.youtube.com/watch?v=dimyrj5oFCE&list=PLmR34ZNlknNY5ns-B9UAGXllF2UPGh3M1&index=2

Ok. Now we are at the core of the whole crafting. The Terra Blade requires a TON of luck, a TON of patience and a TON of preperations. You will see what I mean because this chapter is going to be very long.

This is a short list of what you are going to need:

Buildings:

• Adamantite Forge / Titanium Forge
  
• Mythril Anvil / Orichalcum Anvil
  
• Iron Anvil / Lead Anvil
  
• Demon Altar / Crimson Altar
  
• Hellforge
  
• Furnace

Ingredients:

• 120 Chlorophyte Ore
  
• 12 Hallowed Bars
  
• 12 Jungle Spores
  
• 12 Stingers
  
• 1 Broken Hero Sword
  
• 20 Obsidian
  
• 60 Hellstone
  
• 30 Demonite Ore / 30 Crimtane Ore
  
• 20 Soul of Might
  
• 20 Soul of Sight
  
• 20 Soul of Fright

In the following steps I will show you how to craft / find the swords you need. A quick overview:

• True Excalibur
  --> Excalibur
  
• Broken Hero Sword
  
• True Night's Edge
  --> Night's Edge
  -----> Blade of Grass
  -----> Muramasa
  -----> Fiery Greatsword
  -----> Light's Bane / Blood Butcherer

Excalibur
You craft this sword by using 12 Hallowed Bars on the Mythril Anvil / Orichalcum Anvil.

---

You have to smelt the 120 Chlorophyte Ore in the Adamantite Forge / Titanium Forge to get 24 Chlorophyte Bars.

---

By putting these 2 things on a Mythril Anvil / Orichalcum Anvil together you will get the True Excalibur.

You will get this item from Mothron by a chance of 25%.

---

Mothron is Mini Boss which spawns during the Solar Eclipse Event. This event has a 5% chance to happen on any dawn. Mothron can spawn more than one time, independent from if it was defeated or not.

Night's Edge
This sword is made out of 4 different swords:

• Blade of Grass:
  You craft this sword by combining 12 Stingers and 12 Jungle Spores on the Iron Anvil / Lead Anvil.
  
• Muramasa:
  This sword can only be found inside the Dungeon inside a Golden Chest / Golden Lock Box.(Picture 11) These can be opened with a Golden Key, which can also be found in the Dungeon in other 'free' Chests.
  
  
  
  Picture 11: Golden Chest and Golden Lock Box
  
• Fiery Greatsword:
  You craft this sword by combining 20 Obsidian and 60 Hellstones in the Hellforge to get 20 Hellstone Bars. These can be used on an Iron Anvil / Lead Anvil to craft the Fiery Greatsword.
  
• Light's Bane / Blood Butcherer:
  These swords can be crafted by either smelting the 30 Demonite Ore in the Furnace to get 10 Demonite Bars or by smelting the 30 Crimtane Ore to get 10 Crimtane Bars. When you use one ore the other on an Iron Anvil / Lead Anvil you will get the Light's Bane / Blood Butcherer.

Finally, by combining these 4 swords on a Demon Altar / Crimson Altar you will get the Night's Edge.
The True Night's Edge can then be crafted by combining the Night's Edge, 20 Soul of Might, 20 Soul of Sight and 20 Soul of Fright on a Mythril Anvil / Orichalcum Anvil.

---

The Terra Blade can finally be crafted. You just combine the True Excalibur, Broken Hero Sword and True Night's Edge on a Mythril Anvil / Orichalcum Anvil.

The Seedler can be obtained by defeating Plantera, a Boss which can be summoned in the Underground Jungle. The sword has a chance of 14.29% to drop after the fight.

Plantera:
After defeating the 3 Mechanical Bosses, Plantera's Bulbs (Picture 12) will begin to spawn in the Underground Jungle. By breaking them, Plantera will spawn.



Picture 12: Plantera's Bulb

Guide on how to defeat Plantera by WaffleTime:
https://www.youtube.com/watch?v=imkJ2Zx5edg&list=PLmR34ZNlknNY5ns-B9UAGXllF2UPGh3M1&index=5

You obtain this sword by defeating the Pumpking during the Pumpkin Moon Event. The chances of this sword beeing dropped are


The Pumpkin Moon Event can be summoned by using a Pumpkin Medallion only at night.

The Pumpkin Medallion can be crafted by combining 30 Pumpkins, 5 Ectoplasm and 10 Hallowed Bars on a Mythril Anvil / Orichalcum Anvil.

At this point you have to defeat the Golem Boss to obtain the rest of the swords.

Guide on how to defeat Golem by WaffleTime:
https://www.youtube.com/watch?v=bX6FYpDNIcg&list=PLmR34ZNlknNY5ns-B9UAGXllF2UPGh3M1&index=6

You can obtain the Influx Waver during the Martian Madness Event by killing a Martian Saucer with a chance of 16.67%. This event can occur after defeating the Golem. You can summon this Event by being seen by a Probe (Picture 13) which spawns in the outer thirds of the map and let it get away. Then the Event starts.




Picture 13: Martian Probes

Guide on how to defeat the Martians / the Martian Saucer by WaffleTime:
https://www.youtube.com/watch?v=9C16ofcrr_I&list=PLmR34ZNlknNZ1YRN40j_G1XJRz9rMJs_M

These swords can be obtained after/while defeating the Moon Lord, the endboss of the game.

Guide on how to defeat Moon Lord by WaffleTime:
https://www.youtube.com/watch?v=TICSy5BEaHI&list=PLmR34ZNlknNY5ns-B9UAGXllF2UPGh3M1&index=9

The Star Wrath has a chance of 11.1% to be dropped by the Moon Lord.

The Meowmere has also a chance of 11.1% to be dropped by the Moon Lord.

After gathering all the swords, the time has finally come. Just combine every sword you crafted on a Mythril / Orichalcum Anvil to finally get your Zenith.

CONGRATUALTIONS! YOU JUST MADE THE BEST SWORD IN THE ENTIRE GAME!


If you liked this guide make sure to like it. I had a lot of fun writing it and would do it again sometime.
If you still have questions just ask them in the comment section.

Links:

Insanemind:
https://www.youtube.com/channel/UCztWgPsp2o6qwg2UHdYy9iQ

WaffleTime:
https://www.youtube.com/channel/UCbXiWfLHx2MQc4eXW5-9xIw