Mine Games

A van arrives at a gas station, where a nearby newspaper announces an "unidentified girl found dead in forest". The van belongs to a group of seven friends â Michael, Lyla, TJ, Claire, Lex, Rose, and Guy â who are traveling to a mutual friend's cabin in the woods for a vacation. Michael, who is driving, gets lost in the dark and swerves to avoid a waving figure in the road. The van crashes, which forces them to travel on foot. They arrive at a well-furnished cabin where Rose finds a written note telling "TJ, Lex, Claire" to wait there for them, so they assume that this is the house.
The group enjoys themselves in the comfortable cabin, with the exception of Michael, who sleeps early and has nightmares. The next morning, TJ discovers an abandoned mine nearby and takes the group inside to explore. TJ and Guy, as a joke, briefly lock Michael inside an enclosed cell, which causes him to panic. Rose, who is a psychic, is uneasy about the mine and at one point feels someone grab her leg, though it cannot be one of her friends.
Michael and his girlfriend Lyla return to the van to collect Michael's anti-psychotic medication and confirm that the van is unusable. They find blood on the van's fender and assume that they hit an animal the previous night. Upon returning to the house, the group collectively agrees to stay one more day to wait for the owners of the house. Over the day, Rose has fits and visions of her friends in various stages of death and injury.
While exploring the mines again, TJ and Lex discover three dead bodies that appear identical to theirs and Guy's. They inform the others, and the group reluctantly agrees that something supernatural is occurring. TJ and Lex return to the mine in search of answers and find a traumatized Claire locked inside a cell; she claims that it is Michael's doing. TJ and Lex refuse to save her, knowing that "their" Claire is still in the house, a decision that Claire later supports. Despite Lyla's protests, the others debate whether Michael needs to be locked up overnight for their protection. Unnerved by his passive acceptance of his fate, they put him inside one of the mine's cells.
Michael escapes from the cell, which leads to a chase inside the mines, during which Michael causes TJ and Lex's deaths and locks Claire up inside a cell, where she meets the alternate version of herself. Inside the house, Rose succumbs to poisoning and dies. Guy and Lyla agree to flee, leaving behind in the house a written note for "TJ, Lex, Claire" to wait there for them. Upon reaching the main road, Guy tries to wave down an oncoming van, causing it to swerve and hit Lyla. Guy recognizes the occupants of the van as "them" from the night before and realizes that they are inside a causality loop. He promises the seriously injured Lyla that he will break the cycle.
Guy rushes back to the house to warn the others but is stopped by Michael, who kills him. Michael continues the cycle by warning his past self that his friends will try to kill him, and that when they lock him inside a cell for the second time, he has to defend himself. Michael gives his past self the key to the cell and forces his past self to burn his anti-psychotic medication.
The cycle restarts as the group's van arrives at the gas station at the beginning of the film. However this time Lyla from the previous cycle is still alive, and she hobbles towards her counterpart in the hopes of warning her and breaking the cycle.

Question: Who promises Lyla they will break the cycle?
Answer: Guy