The creature has a magical power that deals [1d6 x CR] damage on a successful magic attack roll (range 30 meters) against a single target. If you prefer to roll fewer dice, convert half the d6s into an equal number of +3 damage bonuses (8d6 is equivalent to 4d6 + 12). Alternatively, the power deals the same damage in a 10-meter-diameter area; a successful DC 10 Dexterity check allows targets to halve the damage.