You'll encounter Yang and Mom Bomb on the Summit. The fight with Mom Bomb has several parts, and can be dangerous if you're not careful. Eventually the small bomb will become larger, and eventually explode. Edward can Hide to avoid the damage, but the rest of the party will be hit hard. Fortunately you have plenty of healers available. Cecil's Dark and Yang's Kick can make short work of the three Bombs that appear, and significantly weaken the three GrayBombs. Be sure to heal up after the fight.