MASSIVE SPOILER WARNING FOR AN UPCOMING GAME! IF YOU DON'T LIKE SPOILERS, PLEASE DO NOT READ.
Also read Alice the Orangutan for more information on the other characters of the AU.
Rain is a humanoid animatronic based on Rain (the child). Her mother designed the animatronic as a double-up animatronic-costume, but... things happened, and Rain (child) was killed in the suit and possessed Rain (animatronic).
She appears in Five Nights at Rain's which will be a game (at some point, since the creator is still stuck on modelling the eyeballs.)
The comic can be seen at Rain's DeviantArt.
Rain as a child was kind-hearted and had lots of friends, but obviously couldn’t resist the temptation to show off about the new animatronic (cut her some slack guys, she was only 6).
As an animatronic, she is vengeful and disturbed. She was tricked by a tape made by Afton, telling her that the spirits of her and her friends would be freed if she killed the nightguard, so she targets the nightguard. But it never worked. If you manage to befriend her and reveal that the tape was a trick on Night 5, she will become more friendly towards you, and you'll team up to kill Afton.
Rain starts in Rain's Service Room. From there, she will climb into the room's vent and wander around the vents trying to find you. Unfortunately for you, she has a good sense of direction. You can distract her by playing audio of children, at which point her safety will kick in and she will try to find them to prevent them from being murdered or hurt. However, Rain will begin to realise it's a trick on Night 4, and will fall for it less. Here's a description for you.
Night 1: Rain will fall for the audio trick every time.
Night 2: Rain will ignore the audio trick extremely rarely.
Night 3: Rain will uncommonly ignore the audio trick.
Night 4: Rain will ignore the audio trick most times.
Night 5: Rain will almost always ignore the audio trick.
If Rain reaches the vent behind you (signalled by vent banging and seeing her on the Monitor), you must shine the flashlight into her eyes. This will always restart her systems and she will crawl back to Rain's Service Room.
On Night 4, a door will be installed, and your flashlight will be taken away. When you hear vent banging and see Rain on the Monitor, you must immediately turn backwards to the vents and shut the door. A bang on the door will signal Rain's retreat.
If you fail to stop Rain, the camera view will force you to look at the vent if you aren’t there already. She will launch out from the vent, and open her faceplates while emitting a horrific scream and jerking her head around violently. This will cause a game over.
On Night 5, you have an option to go poking around in the drawers. This will reveal the tape that Rain heard, telling her to kill nightguards. You then have an option to open all the doors and let Rain in, which will then start a dialogue with her. Then begins a multiple-choice roleplay-thingy, where you have to choose the right option to survive, and to convince Rain that she and the others were tricked. If you succeed, a minigame will play where you have to help Rain and the others kill Afton.
Afterwards, you will burn down the pizzeria. You can choose to make your escape, or stay at the pizzeria to die. It doesn’t really matter which of these you choose, as by this point you will still get the good ending - it just decides whether you will live on, or whether your spirit will go with the animatronics. You know you have gotten the good ending if you see the animatronic heads (and your security cap, depending on whether or not you chose to burn with the pizzeria) with the eyes black, similar to the FNaF 3 good ending. However, if you fail the multiple-choice-roleplay-thingy, Rain will kill you.
If you play Night 5 as normal and don’t choose to convince Rain that she and the others were tricked, you will get the bad ending. You will see a cutscene with you, Afton and the animatronics - portrayed and crying children - separated by a wall, with the bots on one side and the humans on the other. As you and Afton walk off the screen, the crying children will be replaced by their suits, also crying (although no tears are falling for obvious reasons). You will then get a picture of the animatronic heads with their eyes glowing, signifying that the children will be trapped in the animatronic suits forever.
Rain was the daughter of a Bot Entertainment franchisee. The restaurant in question had become very popular and everything was going well. But then, one of her closest friends was found dead outside of the pizzeria, the night after another friend's birthday party.
Rain's own birthday was coming up, and while she was sad, she was also excited for the party. As the courts had decided that Bot Ent. had nothing to do with the murder and that they would continue investigating elsewhere, the pizzeria was open for business.
Rain had a great day. She took her Golden Freddy plush (which would talk to her from time to time) and play puppet shows with her friends' lifeless dolls. She played with the animatronics. And she waited for her mother to announce the new animatronic, as she had promised she would.