The tattoo-based system for temporarily borrowing spells and skills, now extended to dead crawlers.
Edgar lays out the rules as they stood: the ink Carl had, made with Toraline, allowed one to borrow spells and skills temporarily from willing subjects, and to take them permanently from unwilling subjects.
With Milk's help, Edgar has extended the system. His new Essence Ink captures the essence of a fallen crawler and allows the bearer to learn one of that crawler's spells or skills — temporarily, as far as he knows, with no time to experiment toward permanence. Rosetta suspects the Dungeon Anarchist's Cookbook book of Voodoo Donut carries could share skills and spells the same way with the same ink.
The mechanic that puts a dead cleric's spell into Donut's arsenal in time for the assault.