This will be a long one but I can't physically explain it any shorter without losing what makes it so damn creepy.

So, I've only ever had two proper nightmares that were enough to wake me up, one was a generic creepy silent hill sort of affair but the other well that's pretty inexplicable. Shits still stuck in my mind as clear as anything today and this was 5/6 years ago.

So I'm having this dream I'm a police investigator and I'm with my partner (a completely fabricated person my heads just made this guy up) and we've been called out to this house (I know where this house is IRL it was near my old school I know this area like the back of my hand... it's part of a row of houses nothing special just like any other). Anyways, In the dream I think there had been a murder so we are going to investigate and we start in the front garden, so we're chatting and I've got my notebook out and we're looking through bushes and stuff for evidence and having a joke around and something causes me to look straight round to my partner (you know that way sometimes something just makes you look somewhere and you can't explain it, well this except in a dream, that's how vivid this nightmare is)...

And this next part happens in the blink of an eye, this is one of the most disturbing things my brain has ever put to me.

So I turn round and I can see a sort of outline around my partner overshadowing him and in a split second he gets torn in half and the midst of screaming and shaking my eyes are focusing in and this figure is becoming clearer and I'm noticing it's a tail that's split him in two and it's a deep maroon/scarlet colour and its razor sharp and I'm following it up with my eyes and there's this humanoid figure but distorted and it looks like a person with no skin it's such a deep red but it's huge and overbearing and parts of its body look shiny like a xenomorph and then my eyes make it to the face. God I'll never forget that face I can't even describe it I've never seen anything like it so human but so distinctly inhuman at the same time. And everything slows down, I've came to terms, this is how I die... And it looks me dead in the eye and slow as anything it smiles at me and vanishes into thin air.

This is when I wake up, in the midst of shooting straight up in my bed and I'm cold as ice and sweating all over and shivering and I take a moment and compose myself and I realise holy shit I've just seen the devil in a nightmare and it's not like anything I've seen anywhere this is my version of the devil I've made this one up no horns or hooves or part goat shit nothing I've seen in films or books this was unique.

So I get back to sleep and wake up the next day and I tell my gf at the time when she wakes up and she's asking some details and when I tell her where the house is her face drops and she says "Weclome that's the house my gran's friend was killed by her husband in and her body was hidden under the floorboards for years before they found it".

My heart sunk... I had heard her sort of mention this story before but only very briefly there was never a mention of where it had happened. I knew nothing about that house just that it was there. There's no way I could have known. Wtf has happened in the last 8 hours?!

Anyway so yeah that's my input I'd kinda forgotten about this but reading some other comments reminded me about it.