To make certain weapons for characters in Tales of Arise, you will need to gather various materials, one of which is called Bizarre Megacore. To get Bizarre Megacores, you will need to progress until you reach the Underwater waterway.
In this area, you will be able to get the Bizarre Megacores from Ooze enemies. However, once again, like with most loot drops, they are rare, and so it may take a few tires before you get Bizarre Megacores as a drop.
Luckily farming enemies in Tales of Arise is simple. Start by clearing all Oozes in the Underwater waterway, then after the last Ooze is killed, fast travel back to the Underwater Waterway.
Doing so will allow you to reset the spawns for all enemies and farm Oozes for their material drops, including Bizarre Megacores.
You can also rest before going on a farming run and use one of the recipes that increase loot drops to increase your chances of getting Bizarre Megacores
That said, once you have enough Bizarre Megacores, you can head back to a blacksmith or merchant to use the materials to make whatever item requires it in its recipe.
Check out some of our other Tales of Arise guides!