Terabyte672 | Golden Sun - Miniboss: Venus Djinni (Quartz) @Terabyte672 | Uploaded July 2009 | Updated October 2024, 8 hours ago.
After getting Force, the party heads off to the "evil forest" Laurel mentioned after Tret was healed. Force allows Isaac and co. to repel the monsters that live there, and they continue on through it.

You will encounter Quartz on the way to the forest's exit.