In VN’s novel Ada (1969) the element that destroys Demon Veen (Van’s and Ada’s father who perishes in a mysterious airplane disaster above the Pacific) is air:
Numbers and rows and series — the nightmare and malediction harrowing pure thought and pure time — seemed bent on mechanizing his mind. Three elements, fire, water, and air, destroyed, in that sequence, Marina, Lucette, and Demon. Terra waited. (3.1)