Shisu

At a certain point of Breath of Fire III, you'll need to make Shisu.

The ingredients are as follows;

Mackerel - caught at the fishing spot near Maekyss Gorge. It will only appear after talking to the couple there about Shisu, after having visited Parch and spoken to the Mayor. The Mackerel will always be the largest one you've caught, even if you've since sold your entire stock and caught another one (ask me how I know this). Aim for one 68cm or longer.

Shaly Seeds - use Peco to knock some off the tree behind the hut in Maekyss Gorge. You'll need fifteen, so twice should be enough.

Horseradish - on Ogre Road. Use Ryu's sword to slice them. You'll need seven. Enter and leave to make it grow again.

Vinegar - go back to the Cafe, near Momo's tower, and have Garr speak to the person by the well. Play the minigame to get vinegar. You'll need four, so once or twice should be enough.

Finally, speak to the lady at Maekyss Gorge again, then head back to Parch and speak to the Mayor's assistant. You'll be taken to another screen where you can make the Shisu.  The recipe is as follows;

Click on the Mackerel (again, you should have caught one at least 68cm long).  Add fifteen Shaly Seeds, seven Horseradish, and four Vinegar, then knead twice.  Note that you'll only get a visual the first time you click 'knead'.

You should get a Shaman's Ring for this.

The full list of rewards is as follows, in order from best to worst;

Shaman's Ring
Lacquer Armour
Barbarossa
Sage's Frock
Wisdom Fruit
Wisdom Seed
Ammonia