The Gateway of Doom

From Author Wars - https://authorwars.com/books/the-gateway-of-doom-2552758.html

Overview:

Title: The Gateway of Doom
Author: Herbie Brennan
Year: 1984
Type: Novels
Series: Grail Quest (J. H. Brennan)
Number in Series: 3

Variant Titles:

1984. The Gateway of Doom