A cowhide scroll brings the two of them into another dimension, which is bound by strange rules. The pen writing reminds them that they must abide by the rules completely, otherwise they will only become "their" food.
"We know the rules exist, and they probably know them too."
"In other words, part of the rules are used to check and balance them, and the other part is to induce everyone to gradually become their food."
Concept: There is always a shadow of reality in a false world.