My take on the merman from The Cabin in the Woods 2011
A group of kids go to a remote cabin in the woods where their fate is unknowingly controlled by technicians as part of a world-wide conspiracy where all horror movie clichés are revealed to be part of an elaborate sacrifice ritual.
The Cabin in the Woods is a 2011 science fiction[4] comedy horror film directed by Drew Goddard in his directorial debut, produced by Joss Whedon, and written by Whedon and Goddard.[5] It stars Kristen Connolly, Chris Hemsworth, Anna Hutchison, Fran Kranz, Jesse Williams, Richard Jenkins, and Bradley Whitford. The plot follows a group of college students who retreat to a remote cabin in the woods where they fall victim to a variety of monsters while technicians manipulate events from an underground facility for a global purpose.
In an underground laboratory, engineers Gary Sitterson and Steve Hadley discuss a mysterious ritual, after a similar operation in Stockholm just failed, leaving only their facility and one in Japan to undertake the process, with the latter holding a perfect record.
American college students Dana Polk, Jules Louden, Curt Vaughan, Holden McCrea, and Marty Mikalski are spending their weekend at Curt's cousin's cabin in the woods. From the lab, Sitterson and Hadley remotely control the cabin and manipulate the students by intoxicating them with mind-altering drugs. In the cabin's cellar, the group finds bizarre objects, including the diary of Patience Buckner, a cabin resident abused by her sadistic family. Dana recites incantations from the diary and inadvertently summons the zombified Matthew and Judah Buckner.
Hadley releases pheromones to induce Curt and Jules to have sex outside. The Buckners attack them, and Jules is decapitated while Curt escapes. Marty discovers concealed surveillance equipment in his room before being stabbed and dragged off by Judah. The lab workers learn that the site in Japan has also failed, meaning that the American site is humanity's last hope. Curt, Holden, and Dana attempt to escape in their RV, but Sitterson triggers a tunnel collapse to block them. Curt attempts to jump a ravine on his motorcycle to seek help on the other side, but crashes into a force field and falls to his death. Dana then realizes that their experience is staged and controlled. Holden is killed by Matthew while driving the RV, causing it to crash into the lake. Dana manages to escape, but she is quickly found and brutally attacked by Matthew.
The lab employees celebrate the success of the rite, believing that Dana is the only survivor. Having previously dismembered Judah, Marty returns and helps Dana escape from Matthew. He takes her to a hidden elevator, and they descend into the lab and discover an extensive collection of monsters in cages. Dana correlates them with the objects in the cellar and realizes that the objects determine which monsters are released. Cornered by security personnel, the pair release all the monsters, which wreak havoc and slaughter the staff; Hadley is killed by a merman and Dana accidentally stabs Sitterson.
Dana and Marty discover an ancient temple, where the facility's director confronts them. She explains that annual human sacrifice rituals are held worldwide to appease the Ancient Ones, a group of cruel subterranean deities. Each region has its ritual, and the American ritual involves the sacrifice of five archetypes: the whore (Jules), the athlete (Curt), the scholar (Holden), the fool (Marty), and the virgin (Dana). The order is arbitrary as long as the whore dies first and the virgin dies last or survives.
The director urges Dana to kill Marty and complete the ritual, but as Dana considers it, a werewolf suddenly mauls her. Marty shoots the werewolf and scares it off, but the director attacks him. Patience arrives and kills the director before Marty kicks them into the pit below. Deciding that humanity is not worth saving, Dana and Marty apologize to each other and share a joint as the temple floor collapses and a giant hand emerges from the ground, destroying the facility and the cabin.