You’ll find the Kingsblade in a secret room in Estard Castle. You need the Ultimate Key to open this room, so you’ll only be able to get it near the last parts of the story. This optional item can’t be found or bought anywhere else in the game.

Warning: this guide has minor spoilers for Dragon Quest VII.

Finding the Ultimate Key

You’ll find the Ultimate Key in the basement of the Cathedral of Light, which appears on the map after reviving The Almighty.  You can get it the first time your party goes there with the king.

When the king leaves your party alone, exit through the south stairs, go to the first plant and head to the northeastern room. From here, go up again and take the exit south.

Circle all around the cathedral going through a corridor, a room and another corridor. When you reach the northwestern room, take the stairs down.

You’ll be at the cathedral’s prison. Open the blue door on the northern side of the room. There are two chests in here. One chest has a Haywire Helm, and the other has the Ultimate Key.

You can use the key in this same room to open all the prison cells. Break the pots there to get a Seed of Magic, a Seed of Life and a Seed of Strength.

Note: if you don’t get the key at this point of the story, you can revisit the cathedral later on, but there will be monsters in the entire place.

Getting the Kingsblade

Now that you have the Ultimate Key, you can open every single door in the game. Head to Estard now, and go to the castle.

If you rotate the camera to see the back of the central stairs, you’ll find a hidden staircase that goes to a basement. Go down those stairs.

Now you just have to open the locked door with your Ultimate Key and you’ll find four chests. Open them all to get a Mini Medal, a Seed of Strength, a Platinum Shield and the Kingsblade.

Congratulations! The Kingsblade is yours. This sword has excellent stats for this point of the game. It can only be equipped on the Hero or Aishe.

Considering that the Hero already has access to decent weapons at this point, like the Sea Serpent Sabre, it’s a good idea to give it to Aishe, as it will be a good while before you find a stronger weapon for her.