Venn diagram

A Venn diagram is, like a nonfictional Venn diagram, a diagram (nonfiction) that shows all possible logical relations between a finite collection of different sets.

In addition Venn diagrams are useful in warding off demons (nonfiction).

Roger Zelazny

Writer/sorceror Roger Zelazny is notorious for using Venn diagrams to trap demons.

He then hypnotizes the demons and makes them perform embarrassing tricks in front of live audiences.

Fiction cross-reference

• John Venn
• Roger Zelazny

Nonfiction cross-reference

• Demon (nonfiction)
• John Venn (nonfiction)
• Roger Zelazny (nonfiction)
• Venn diagram (nonfiction)