Buffy and Spike go to hell dimension

I loved this story! They go to hell, but time is different and end up living there. Set around season 4 I think.

Is it The Writing on the Wall by Holly

I think you are talking about

The Writing on the Wall by HollyDB

https://www.spikeluver.com/SpuffyRealm/viewstory.php?sid=32668&warning=NC-17

Summary: There was no body to bury. There was no funeral. There was nothing but the three rules and the knowledge that a thousand years of torment was nothing compared to a world without her in it. Spike embarks on a journey through the Gates of Hell to rescue the one he loves, but in order to save her, he must risk losing himself.
Timeline: Post-The Gift, AU.

Hmmm...if it's set in season 4, then it can't be 'The Writing on the Wall'.

But I do remember a story (set in S4) where Buffy was sent to Hell to retrieve a necklace in order to stop a demon from opening the Hellmouth; and Spike went with her. They made friends with Satan's daughter and even had jobs in Hell. There was also a scene where they were given powers of ice and fire.

I just can't remember the title.

soii thats the one I'm looking for. They go for an amulet and get stuck for a while. They wrestle a runaway demon and get powers of fire and ice. hey have another demon friend that gets married and her heart in her butt cheek(LOL)

kimdawn
The fic you are looking for is To Hell and Back by Palerider. It can be found here, but is a WIP and I don't know if it was ever finished and if it was I dont' know where to find it.

To Hell and Back by Palerider is completed at adultfanfiction dot net.

To Hell and Back by Palerider

here's the link to fanfiction.net - but both this version and the one here on SR have 34 chapters.