Instructions
Touch the Crystal bug. To complete its ruse, the fiend will remain quiet and unassuming (like a normal save crystal) until touched. Once activated, the attack will begin.
Take inventory of your party's health and strength. As magic will have no effect on this particular fiend, you will want to use your heaviest hitters with the highest levels. HP should be full on each fighter.
Retreat from the Crystal bug to rearrange and replenish your party. Since this enemy is a stationary creature, it will not be able to pursue you. This will make it easier to retreat when necessary.
Fight the Crystal bug with a barrage of physical attacks. This fiend will absorb or resist any magic sent its way, so MP should be reserved for healing your party.
Continue the retreat and replenish process if necessary. Continue with the physical attacks until the Crystal bug is finally defeated.