I have multiple theories about this game. Here is few:
His sister dated some boyfriend that gave her a necklace and maybe killed her, although there is a word accident mentioned. I will date who ever I want is refferd to the father of the boy (her stepfather) since her father died (kiss your father for goodbye). teleports are also build like necklace. So it is important part of the story for sure. The thing is that she did something wrong that diserves hell. There is a line when she sais I am sorry I didn't mean to do that or something similar. Maybe she was just mean to him and that is it. But the line it was you suggest that he actually killed her, there is also don't do that line.. But it could be interpreted as he commited suicide and beffore he do that she is saying don't do that. Another theory is she committed suicide witch fits in as a reason for hell. I agree that religion is not a motive but hell is part of religion so maybe there is a lil bit of it. Now stairs have maybe something with it but maybe it is just for gameplay since you are trapped in a cube. And another thing maybe necklace is intended to be her 18th birthday present that she never got, but line o I remember this doesn't fit very well then. There is a line this is not my memory can suggest that with necklace that she never saw it that boy remembers it and now she got it and she is complete. When my grandfather died my uncle was very sad because he traveled from different town and wanted to bring some extra good (and expensive) type of sausage than my grandpa liked for him. He brought sausage but grandpa died while he was along the way. SO on the funereal uncle was feeled depressed that he didn't succeed to bring him those sweet sausages. And he was repeating I should go earlier.. if I did I would brought him that on time etc. Remorse. Maybe it is thing with necklace. It was meant to her but she never got it because of fight with her stepfather or she didn't want to accept it due to jelousy, or her brother wanted to give her...
And what does "Sequester" means? Isolation or separation or confiscation? In this case what fits best can some1 tell me? Maybe he took her that necklace or they are separated and now they are 1 or necklace and she are one. For sure boy is bringing necklace to her since there is level when he picks It up..
The necklace also looks like a chain by the way. When the sister told the boy to touch the necklace it kind of feel like the sister was trying to trap the boy; but in the end the boy voluntarily decided to stay with sister/save sister by sacrificing his life i guess? Cause he jumped into the lava with "faith". But he didn't ended up staying (woke up instead),and he left the necklace/chain on the grave.
I'm assuming the grave is his sister's, the last shot which was the necklace on the grave, kind of represents his sister was still chained would never be free
