The piranhax is, as the name suggests, a monster similar to the piranha fish. You can find it somewhere in the Pentelas region.
Piranhax's location in Xenoblade Chronicles 3
Fans of the Xenoblade Chronicles series will be happy to know that one of the original monsters has made its way into Xenoblade Chronicles 3. This monster is none other than Piranhax. This time though, you have to hunt Piranhax to get Rich Fish Meat which is part of a quest.
In this guide, I'll show you exactly where to find Piranhax.
In the first stages of the game, you will receive a quest called Collectopaedia Cards from Roald. He will ask you to collect a bunch of items which include 3 Tough Radishes, 3 Clusters and 2 Rich Fish Flesh. As for the latter, the only way to get them is by hunting Piranhax.