One use only. A Wizard can declare that he is using Neferra's Scrolls of Mighty Incantations immediately before casting a spell. If he does so, the Wizard must add a number of extra bonus dice, equal to his Wizard level, to the power dice he is going to roll (you still need to roll at least one dice from the power pool). The bonus dice do not count as power dice. However, a roll of any double when casting a spell using them will cause Irresistible Force (and a Miscast).