The Ultima Blade is, you guessed it, the ultimate weapon in Final Fantasy XV. This is a trademark of the series is usually takes some effort to get it. Noctis has his own Ultima weapon, which is an upgrade of his starting Engine Blade weapon.
I’m going to go over how to upgrade the Engine Blade to the Ultima Blade, as well as what you need to do so.
Upgrading the Engine Blade
You will need to upgrade the Engine Blade 3 times to turn it into the Ultima Blade. You can start this process as early as Chapter 2 by getting a quest from Cid called, A Better Engine Blade. The final part cannot be done until at least Chapter 6.
A Better Engine Blade
This quest requires you to bring a Rusted Bit to Cid, along with the Engine Blade in your inventory to be upgraded.
The Rusted Bit is very common and I actually got one around the Hammerhead area. You will also get one as you go through the story, in the Keycatrich Dungeon.
Once you turn it in you will get the upgraded Engine Blade II.
A Better Engine Blade II
This becomes available once you complete the previous quest and requires you to get a Glass Gemstone.
You can also find these commonly, but you can definitely find one in Lestallum.
When you turn it in, you will have to wait for Cid to finish upgrading before you get it. Just do a quest or hunt and Engine Blade III will be ready for pickup.
A Better Engine Blade III
The last part becomes available when you have finished the previous quest. This one upgrades to the Ultima Blade, and requires a rare material.
You will need to bring Cid a Sturdy Helixhorn, which you can get from Duplicorns.
The best way to find these enemies is a Hunt in Old Lestallum.
It is southwest of Lestallum on the map.
Just start your drive going west, and keep going south until you reach it. It is south of the parking spot at Tollhends Stronghold.
The Hunt with the enemies is called The Last Spiracorns.
This is a level 29 hunt that requires you to hunt 2 Duplicorns and 3 Spiracorns. You can repeat the hunt until you get the Sturdy helixhorn, which are dropped from Duplicorns.
Make sure you target the Duplicorn and break its horn. You can do this by warp-striking until “Break” comes up on the screen. It is not guaranteed though.
NOTE: You need Sturdy helixhorn and not the Crooked helixhorn.
Once you get the helixhorn, return to Cid to have him upgrade your weapon. Make sure you do not have the weapon equipped when you do so.
Also, be aware if you have quests to upgrade other weapons. You can only give Cid one item at a time, so if you have the required materials to upgrade other weapons, he might ask for those first.
If it asks you to turn in another material, the only way around this is to sell the material if you do not want to wait.
Some materials may be rare, so you might want to just turn them in and get the upgrade until it asks you to turn in the helixhorn. Just complete quests or hunts until they are ready.
You will have to wait while Cid upgrades the sword, so complete 5 side quests or Hunts and the weapon is ready. You will need to rest somewhere before he will tell you it’s ready.
Now that you have the Ultima Blade, you can make all those dungeons and Hunts much easier. Let me know if you have any questions!