Lex possessed the Fire Enchantment, but the duration of this spell was too long. That would cause Bain and Cuisi, who were hidden below, to be defenseless. The attack this time around was an experimental one. If it was effective, and the Fire Blast was resolved, then this level-6 magic scroll would be much cheaper than a level-7 scroll.
Lex did not have many level-7 scrolls in her possession. Since she did not know how many dwarf demons were there underground, the consequences might be disastrous if she had used all of her scrolls.
"Abominable creatures!"