Incubus: The Horror Cult Classic Filmed in Esperanto

If you were to browse through the forgotten corners of 1960s cinema, you might stumble upon an artifact that defies easy categorization. It is a black-and-white gothic horror film. It features William Shatner just months before he boarded the USS Enterprise as Captain Kirk. It looks like an Ingmar Bergman art film, but it sounds like nothing else on earth.

This film is Incubus (1966), and it holds a strange distinction in the annals of movie history: it is the undisputed “cult classic” of the Esperanto language. While Incubus was intended to be a creepy tale of demons and the corrupted mortal soul, for linguists and language enthusiasts, it serves as a fascinating—and often hilarious—case study in phonetics, constructed languages (conlangs), and the power of foreignness in storytelling.

The Vision: Why Esperanto?

Incubus was the brainchild of Leslie Stevens, the creator of The Outer Limits. The plot is standard B-movie fare: an incubus (a male demon) falls in love with a pure-hearted woman, angering the dark forces of the underworld. However, Stevens wanted the film to feel ancient, mythological, and entirely removed from contemporary American culture.

Usually, when filmmakers want to evoke the “archaic” or the “demonic”, they turn to Latin due to its associations with the Catholic church and exorcisms. However, Stevens felt Latin carried too much specific religious baggage. He didn’t want to use gibberish, as the audience can instinctively tell when a language lacks syntax and structure. He needed a language that was a complete, functioning system, yet possessed an agonizingly obscure “otherness.”

Enter Esperanto.

Created in 1887 by L.L. Zamenhof, Esperanto was designed as an auxiliary international language to foster world peace and understanding. It combines romance and Germanic vocabulary with a perfectly regular grammar. Ironically, Stevens chose this language of “hope” (the translation of the word Esperanto) to script a movie about the forces of hell. The director believed that because Esperanto had no specific country of origin, it would create a “universal” atmosphere—a place that was nowhere and everywhere simultaneously.

Linguistic Irony: The Language of Peace as the Language of Evil

From a sociolinguistic perspective, the choice of Esperanto is jarring. Zamenhof’s creation is inherently optimistic; it is a language designed to bridge gaps. By utilizing it as the tongue of demons and succubi, Incubus inverts the language’s intended pragmatics.

However, the effect Stevens achieved was the Uncanny Valley of Language. For the average viewer who does not speak Esperanto, the dialogue sounds vaguely familiar—like a mix of Spanish, Italian, and Polish—yet just elusive enough to be unsettling. It forces the brain to try and categorize the accent, but fails, resulting in a subconscious unease that serves the horror genre well.

The Pronunciation Disaster: An Analysis

While the concept of using Esperanto was artistically sound, the execution provides endless entertainment for linguists. The cast, including Shatner, Allyson Ames (the Succubus), and Milos Milos (the Incubus), had absolutely no background in the language. They were reportedly given the script with phonetic spellings and had virtually no coaching.

For fluent Esperantists (Esperantistoj), watching Incubus is less of a horror experience and more of a comedy of errors. The pronunciation is notoriously atrocious, highlighting the difficulties of phonetic mimicry without understanding phonology.

The Problem with the “U”

Esperanto phonology is strict. It has five vowels (a, e, i, o, u), and they are pure vowels, similar to Spanish or Italian. The cast, predominantly American, consistently applied English dipthongs and rhoticity to the dialogue.

A prime example is the word Incubus itself. In Esperanto, the word for a male demon is actually Inkubo. The filmmakers kept the Latin ending because it sounded scarier to English ears. Furthermore, the cast pronounces the ‘u’ sound as the English “yew” (like in “cute”). In Esperanto, ‘u’ is always pronounced ‘oo’ (like in “tool”).

Stress Patterns and Rhythm

One of the cardinal rules of Esperanto is that the stress always falls on the penultimate syllable (the second to last). This gives the language a distinctive, bouncing cadence.

• Correct: es-pe-RAN-to
• Shatner’s Method: Following English dramatic stress patterns.

Throughout the film, the actors place stress arbitrarily to heighten the drama. They emphasize words as they would in English theater, destroying the rhythmic flow that makes Esperanto sound like a cohesive language. The result is a choppy delivery that sounds less like a native tongue and more like an incantation read from a cue card.

The Nasal Twang

William Shatner delivers his lines with a distinctive nasal, North American drawl. When speaking the word demonoj (demons), the ‘j’ (which functions as a ‘y’ sound in Esperanto to create a plural diphthong) is often mangled. Instead of a crisp, clear European vowel structure, the cast produces the “schwa” sound found in casual English speech. This linguistic laziness creates a dissonance: the subtitles promise high fantasy, but the ears hear New Jersey.

The Legacy of the “Curse”

Interestingly, the linguistic hubris of the film seems to have birthed a legend. Incubus is often cited as a “cursed” production, a reputation that has helped keep it relevant in cult circles. Shortly after filming:

• Milos Milos (the actor playing the Incubus) killed his girlfriend and then himself.
• Ann Atmar (a supporting actress) committed suicide.
• The film’s master prints were thought to be destroyed in a fire in Paris.

For decades, the film was considered lost, perhaps a victim of the “Devil’s Language.” However, a print was discovered at the Cinémathèque Française in 1996. When it was restored and released to home video, the linguistic community finally got to analyze the curious artifact in full quality. The curse, it seems, did not extend to the removal of the film from history.

Conserving Language Through Cult Film

Despite the butchered pronunciation, Incubus remains a significant cultural touchstone for the Esperanto community. It is the only feature-length horror film ever produced entirely in the language.

In modern cinema, we have grown accustomed to ConLangs. We have High Valyrian in Game of Thrones, Na’vi in Avatar, and Klingon in Star Trek. These productions hire Ph.D. linguists to coach actors on glottal stops and syntax. Incubus comes from a simpler, wilder time in filmmaking. It represents a bold experiment where the sound of a language was treated as a special effect, just like makeup or lighting.

For language learners, Incubus offers a unique lesson: Intention impacts perception. Even though the actors failed the technical requirements of the language, the intent to communicate something otherworldly was successful for the target audience. It proves that in communication, context and atmosphere can sometimes override grammatical precision.

Conclusion

Is Incubus a good movie? That is debatable. Is it a good example of Esperanto? Absolutely not. But it is a magnificent example of linguistic ambition.

Today, apps like Duolingo have made Esperanto accessible to millions, and a modern speaker watching the film will likely cringe at Shatner’s vowels. Yet, there is something charming about the attempt. Leslie Stevens took a language designed for international brotherhood and used it to summon the devil. It remains a bizarre, distinctive chapter in cinema history where linguistics took center stage—even if it forgot to rehearse its lines.