The film's storyline concerns a team of archaeologists investigating Mayan ruins, who come across a creature that is a shapeless, amorphous blob.

In interviews given long after the release of the film, both Freda and Bava gave conflicting opinions on who should be considered the real director of Caltiki.

The film was released in Italy on 8 August 1959, where it grossed less than Bava's and Freda's previous genre collaboration, I Vampiri.

Once there, they find a deep pool of water and a large statue of Caltiki, the vengeful Mayan goddess who was ceremonially presented with human sacrifices.

Fearing for his safety, the group pulls him back to the surface, only to find that his flesh has been reduced to a decayed mass over his skeleton upon removing his face mask.

One of the scientists drives the tanker directly into the moving mass, which violently explodes and sets fire to the blob, destroying it.

At the comet's closest approach to Earth, the remaining piece of the blob removed during the surgery begins expanding to an enormous size and reproducing.

While attempting to convince the Mexican government to send its army to destroy the reproducing blobs, Fielding is arrested but manages to escape.

Fielding arrives just in time to save them, just as the arrayed soldiers lay waste to the creatures with torrents of fire.

[3] Although not mentioned in any credits or ministerial papers, European sources list the involvement of the French company Climax Film in the production.

"[6] Bava described Caltiki – The Immortal Monster as "my very first film", while noting that Freda had fled the set "because everything was falling to pieces.

Mario Bava did take care of the cinematography, the special effects and directed the scenes with the miniatures (that is, mostly the tanks....), and in addition to that he filmed some shots of soldiers with flame throwers.

[13] Arrow's release features both Italian and English audio tracks, two separate audio commentaries by Bava historians Tim Lucas and Troy Howarth, an interview with critic Kim Newman about the film's place in the history of monster films, several archival featurettes, and an alternative "full aperture" presentation of the film that contains more visual information than was present in the original theatrical prints, particularly with regard to Bava's visual effects shots.

[14] From contemporary reviews, The Monthly Film Bulletin commented that "phony sets, bad acting and limitations of a small budget seriously hamper the first half" and that "once the monster asserts itself things begin to liven up.

"[15] Wanada Hale of the New York Daily News referred to Caltiki as a "feeble horror film" and that "Not only the story is bad; so are the production, the direction, the dubbing and the acting".

"[12] In Phil Hardy's book Science Fiction (1984), a review described the film as a "minor outing [...] though the acting is routine and the script leaden, Bava injects a few stylish flourishes.

"[17] Slant Magazine stated that the film "remains an impressive showcase for Bava's inimitable skills behind the camera, in particular his uncanny ability to craft moody atmosphere and some extremely grisly imagery (for 1959, anyhow) out of the simplest and most frugal of cinematic means.