I wonder if the Temple of Fiends was a copy of this

Quite likely. I hear there's a new game being made based on that adventure, but it originally was a AD&D game from long ago. And, of course, a lot of AD&D influence is found in Final Fantasy. Tiamat and Bahamut, for example, are both AD&D gods.
I LOOOOOOVE Flying Omelette!!
Crawl and 1000