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You utilize your mastery of Elementalism to gather dust from the floor and compact it into a dense ball. Then you pick up this ball and hurl it at the gap between the obsidian pillars. There is a loud Crack! and a brilliant flash of blue-white light illuminates the hall when the ball of dust hits and discharges the magical force field.
This burst of violent energy is followed by an abrupt and total silence. After a few moments, you detect a faint humming sound and your Kai Sixth Sense warns you that the force field is recharging.
