You start wondering how it was possible that Robin survived all those years, all alone locked in the basement of an abandoned mansion, however you remember that in the last part of the game Michael receives an eviction notice, meaning that the mansion was sold fraudulently to him, also earlier when he impersonates Christopher Milton while phoning to the bank, with the right dialog choices, he can learn that Blackwood's bank account is still active. All of this point that James Blackwood might still be alive which is confirmed in Last Visit.
It's hinted in the main game that somebody has been feeding him all these years, judging by all the blood stains beneath the window and the meat in the room.
There's a receipt from a butcher shop in one of the places Michael searches, also. For a large order.
Immediately after preparing the main component of the amulet, Michael starts hearing very creepy laughter and an ominous, mocking voice. This seems like it would invalidate the Maybe Magic, Maybe Mundane aspect of the story ... except that he's just been cooking an unidentified plant over an open gas stove that was damaged and left sitting out for years. It's entirely plausible to assume that he'd just unwittingly inhaled a hefty does of psychotropic chemicals and methane fumes, and is suffering from audible hallucinations, rather than it being proof of a curse.
Robin in the Jump Scare ending seems horribly meager for a deformed "monster" chasing the player, until you realize that he's so aged and worn with how long he'd been sealed inside the cell. He's not trying to kill the player (at least, not very well), but drive them straight back out of his cell, which is probably why he quiets down once Michael's gone and almost seems sad that the door's closed on him again.
If the curse was real the evil god sealed in the cursed mask will one day gain strength and break free, since the mask becomes unaccounted for at the end of Last Visit, and there are no more natives to keep it in check.
In the secret ending is a letter which reveals that Milton met his end in the crypt when James locked him inside. That explains why there's a body in what's supposed to be Catherine's casket, while she herself is buried in the garden.
We never see Michael eating anything for THREE days, he even mentions on the first day that he needs to buy some food, except that the events ground him at the manor.
Even more glaringly, he doesn't seem to drink anything in the first two days, because there's no water in the house until he restores it on Day 3. Yet he never even gets thirsty enough to sample the house's liquor stashes.
At the end of the game, there doesn't seem to be any lavatory in the locked part of the basement.
In Last Visit, the character comments on how the basement smells like a cat's been urinating everywhere.
