Director József Gallai asked the actors to watch Rorschach (2015) to fully understand the concept of the film.
The longest version of the script was 87 pages long, while the shortest one was only 73. Eight different versions of the script were written altogether.
This is the fifth collaboration between special makeup effect artist Hanna Erkel and director József Gallai, the others being Bodom (2014), Moth (2016), Echoes (2018) and Parallel (2018).
The painting depicting the Whispering Man was exclusively painted by freelance artist Maria Marachowska.
The first version of the script was finished in April 2018, while the final version was completed in August 2018.