The Valdemar Legacy II: The Forbidden Shadow is the rare H.P. Lovecraft adaptation to feature the author's most famous creation Cthulhu. While H.P. Lovecraft didn't live to enjoy the critical reappraisal of his work, he's considered one of the greatest horror writers of all time. His best works are bleak, claustrophobic tales of mankind being exposed to dark forces outside of their comprehension, which typically drives them insane - or much worse. Some of his most famous stories have been adapted into films like Re-Animator, From Beyond, and anthology Necronomicon.
It's difficult to adapt Lovecraft for the big-screen since most of his fiction is quite short, and the creatures that feature in them are so horrifying they defy description - which is tricky to visualize for a movie. His longest story is At The Mountains Of Madness, which Guillermo del Toro once developed as a big-budget movie with Tom Cruise set to star. Universal opted not to greenlight the project since the large budget and del Toro's insistence on an R rating left the studio nervous about its commercial prospects.
Sadly, At The Mountains Of Madness has yet to happen, though it remains del Toro's dream project. His script also featured a brief appearance by Cthulhu, the cosmic entity that is easily the most popular of Lovecraft's monsters. The being first appeared in the short story Call Of Cthulhu and is one of the author's Great Old Ones, a race of God-like beings who once ruled the Earth. The creature turned up in 2018 video game Call of Cthulhu: The Official Video Game, but it has rarely appeared on the big screen. The Valdemar Legacy II: The Forbidden Shadow from 2010 is a Spanish horror film that didn't back away from the challenge of depicting Cthulhu - though his brief scene is unlikely to satisfy purists.
The movie is a direct follow-up to the original The Valdemar Legacy, which was also released in 2010. The movie mixed together a bunch of elements from Lovecraft's mythology, and even historical figures like Dracula author Bram Stoker appear. The Valdemar Legacy II: The Forbidden Shadow finishes off the story, and features a sequence where a cult invokes the great Cthulhu. Naturally, the deity isn't friendly and massacres a bunch of them before being pulled back into the depths.
The Valdemar Legacy II: The Forbidden Shadow wasn't well-received compared to the original, though its rich production design and creepy atmosphere were praised. The Cthulhu appearance is something of a disappointment, with the deity looking much smaller and less imposing than it should. It's kind of fun to see Cthulhu a smash up the creepy cult, so it's not all bad.