Majora's Mask fanfiction, possible name End of Days, Ragnarok: A Faustian Dilemma
The Ocarina of Time is broken and Link has no way of resetting the 3 day cycle, and in desperation he sells his own soul to obtain Majora's mask for himself. Now being able to physically push the moon back himself, it's a race against time for Link to learn how to use Majora's dark powers whilst avoiding being lost to them and his own growing insanity. Whatever entity Link sells his soul to exploits a hole in the fabric of Time to retrieve Majora's Mask from another time period/universe hence there are 2 of the mask within the same frame of time. One possessed by the Skull Kid and the other by Link. The events of the original game transpire (Link getting the alternate mask just as the moon is about to fall) and the original mask goes inside the moon, with Link and his own mask on the outside. Using Majora's powers Link is able to push the moon back giving him another 3 days, but Majora's mask proves to be extremely sinister if co-operative. Possibly because of Link's status of wielding a piece of the triforce he is resistant to straight up possession, so the mask has to resort to gradually wearing him down and driving him mad. The mask with Link is interested in destroying the other mask as it sees it as a rival, and realizing Link's strength it intends to make him into its puppet. Link is at first hesitant wearing the mask at all, but he becomes reliant on it's power and eventually has it on all the time.
What it meant by, Link selling his soul is that when he dies possession of his soul will go to the entity who summoned Majora. The mask is also motivated to keep Link alive in order to keep his soul for itself, as being wielded by him makes the mask more powerful. The mask also doesn't want the original timeline to proceed as normal, as the original mask is an older version and has somehow gone completely insane, naturally the mask wants to avoid that.
Possible Fatal Frame fanfiction? Black Strands
Unnamed female wanders around mansion, there are multiple spirits of the recently deceased who died of some cataclysm. Most knew the female while they were alive and some are even friendly with her. 2 main hostile spirits roam around and try to corrupt the other spirits ( maybe dragging them to hell?) Along with attacking the female protagonist. Objective aside from exorcising hostile ghosts is to protect non combatants, racing from place to place whenever a friendly spirit is being attacked. Spirit is destroyed if you do not arrive in time.
The female has a camera obscura to fight with, though it is extremely weak possibly due to the quality of film being used. You can also wield spectral arms made of black hair, as the protagonist's soul has been altered in some aspect, may be half dead or a spirit themselves. It is extremely effective, instantly dispersing less powerful spirits if they should come into contact with it. A downside as it harms non combatant spirits. The two main hostile spirits are quite strong and can only be driven off for a period of time before attacking again. Are not interested in killing protagonist, leading towards the idea that she too is a 'corrupted' spirit who has simply lost their mind.