The strain must be too much. Reality is pulling itself apart at the seams and every wizard and sorcerer feels the overpowering energy, unleashing arcane forces in every direction.
Each investigator flips each Spell he has, resolving the effect on its back as if he had rolled only 1's (no successes) on his test.
If the Spell effect refers to "that investigator" or a chosen investigator, the investigator must choose himself. If the Spell effect refers to any other token or space, the investigator must choose the nearest token or space of the indicated type.