Spells delivered by tattoo; the method by which Donut will receive the missing piece of Carl's plan.
Donut expected a spellbook. What Rosetta brought up the Nest Tower instead was Edgar and a tattoo kit — because the spell has to be at least level 8 to work in conjunction with War Crime, and tattooing is how she will get it there. Rosetta produced a pink Bic razor, promised to make it quick, and asked Donut where she wanted it.
Donut, staring at the tattoo implements suspiciously, demanded to know where she wanted *what*.
The tattooed-spell method being used to give Donut the final component of the plan.