Isle Of The Snake People (1971)

Starring Boris Karloff, Julissa, Carlos East, Rafael Bertrand, Yolanda Montes
Directed by Juan Ibanez
(actor & director credits courtesy IMDB.com)

A captain of police tries to establish law and order on an island where the people practice voodoo rites, but in return his men are assaulted and killed, and a powerful curse is placed upon him.

Here's another of the Mexican horror films actor Boris Karloff filmed scenes for before his death, none of which have been critically praised, and this one may well be the worst of the lot.  With an overemphasis on depicting the voodoo rituals at length, including an interminably long opening scene that doesn't make much sense until midway through the movie, there's not much entertainment to be had here.  There are some intriguing scenes with Karloff as a scientist trying to harness the power of the mind, and coming up with a scientific explanation for the zombies on the island, but these aren't followed through on, and what we end up with isn't worth watching.

The Fear Chamber (1968)

Starring Boris Karloff, Julissa, Carlos East, Isela Vega, Yerye Beirute
Directed by Juan Ibanez
(actor & director credits courtesy IMDB.com)

A scientist and his assistants discover a creature made of living rock underground that feeds on the chemical generated in the human body when experiencing extreme terror.

According to IMDB, this is one of a quartet of horror films made in Mexico that incorporated scenes featuring Boris Karloff filmed in America by director Jack Hill.  They would be among Karloff's last films, and do not have a reputation of quality.  This one is certainly watchable, and does an effective job of presenting the terror-filled "fear chamber" the scientists create to shock young women into providing the chemical to feed the creature.  However, while Karloff is always worth watching, the rest of the film doesn't measure up, with poor special effects standing in for the creature, and the transformation of a dimwitted lab assistant into the movie's central villain coming off as pretty comical.