The beast looks like a bird in this version.
The Monster's mansion (which was also used as the residence of the evil astrologer Aldobrandini in The Ninth Heart (1979)) was the largest construction in the long history of Barrandov Studios up to that time. It was only surpassed by a faithful replica of one of the Prague churches in Anthropoid (2016).
Because of the director's decision to build the entire castle in the studio, the budget was so high that Juraj Herz had to shoot a second fairy tale The Ninth Heart (1979), on the same set at the same time. Both films took 90 days to shoot. Parts of the set were also used for Ota Koval's Kocicí princ (1979).
During the filming of the scene when the mad Monster sets the castle on fire, the Barrandov studios almost burned down.
Juraj Herz wished the Monster to speak in the famous velvety voice of Eduard Cupák. But the actor, who has otherwise dubbed hundreds of foreign actors, refused. Eventually, the Monster was voiced by Jirí Zahajský.