Tohl Narita: “At any rate, I wanted to make an utterly black monster. This is a case where the form came along when I decided the color.”
As it is well known among fans, the costume of Magulla was the same as Nelonga that was a monster remodeled from Toho’s Baragon by replacing its head while it was made into Pagos of “Ultra Q” in the first place.
In Magulla’s case, given it is said that the costume was remodeled again into Gavora, it makes an explanation sound more plausible that the costume was wrapped up with the thorny surface so that it could be removed after shooting.
The remodeling work is said to have been done by Akira Sasaki who sculpted several primary Ultra Series characters including the original masks of Ultaman and Ultraseven.
Sasaki himself says in a book interview that he just barely remembers he sculpted only the back part cutting and pasting urethane.
In the same book, Tetsuo Yamamura says the thorns on the back were made of urethane scraped and painted black without latex coating.
If it is true that the costume was wrapped with a removable surface, the same method used for Gomess of “Ultra Q” might have been applied to Magulla.
It is certain that thinking it was a costume borrowed from Toho to be remodeled into Gavara and to be returned to Toho finally makes it least likely that the costume was converted into Magulla by remodeling it so much as the thorny parts were directly adhered to the suit, but the truth remains unknown.
I myself didn’t notice that Magulla was a remodeled monster from Nelonga as a kid while they looked totally different, moreover, partly because Magulla was not such an impressive monster unfortunately as he kept a relatively low profile in the episode if anything.