Borderland

Borderland is a film directed by Zev Berman in 2007.

On a college trip in Mexico a group of friends uncover a religious cult that practices human sacrifice after one of them goes missing.

Very Loosely Based on a True Story, although moreso than other horror films with the same claim; there was a religious cult lead by a man named Adolfo de Jesús Constanzo in Mexico City who performed human sacrifices in order to gain protection in his drug deals. He was arrested after murdering a college student on spring break.

It was part of the After Dark Horrorfest film festival.

Tropes used in Borderland include:

A God Am I: The leader of the cult sees himself as this.
Affably Evil: Randall is pretty charming for a misogynistic serial killer.
Black and Gray Morality: Word of God says this was the intention of the ending in which Ed brutally murders one of the younger, more innocent cult members despite their pleas for surrender.
Cold-Blooded Torture: The cult is fond of this.
Cruel Mercy: Ulises is left alive by the cult at the beginning of the film but one of his legs is broken and his friend is killed to leave a message about what happens to people who cross them.
Eye Scream: Happens to Ulises' partner in the opening scene.
Forced to Watch: Ulises is forced to watch his partner tortured and murdered by the rest of the cult.
Gory Discretion Shot: The film is pretty gory but a lot of the violence happens off-screen and we usually just see the aftermath.
Hey, It's That Guy!: Samwise Gamgee has a darker side that he never showed Frodo.
Hooker with a Heart of Gold: The young hooker that Phil almost hooks up with.
Hubris: The leader of the cult considers himself to be invincible thanks to the sacrifices performed. He is shot and killed by Ulises moments later.
Human Sacrifice: The modus operandi of the cult.
Off with His Head: We don't see it happen, but at one point Phil is decapitated and his severed head is discovered.
Playing Against Type: Sean Astin plays a scumbag serial killer affiliated with the cult.
Police Are Useless: The local authorities are terrified of the cult and refuse to help. Only Ulises proves to be useful.
Redemption Equals Death: Ulises, the disgraced cop, finally kills the leader of the cult but is shot in the process and dies from his wounds.
Religion of Evil: Subverted. The film makes clear that Santería has been perverted by the cult for their own selfish purposes and is not an evil religion by itself.
Sex as Rite-of-Passage: Phil tries to do this with a young prostitute but stops once he discovers that she has a baby.