Buffy jumps to a hell dimension for 150 years

Hello,
I'm looking for a fanfic that takes place at the end of Season 6. Buffy jumps into the portal and ends in a dimension that has to fight two kinds of vampires and monsters. Ends gradually losing the memories even painted the whole band in a cave pareedes. the scooby seek and find a book that says that for 150 the slayer has protected this dimension. Bring it back but she acts more as a survivor than as Buffy.

I read this one just a few weeks ago! Think brain! Think!!!

Is it Longer than Forever by Demonica Mills? http://dark-solace.org/elysian/viewstory.php?sid=460

Yes! Thank you for saving me from any further brain strain!!

Than you!!!!!!!!!!! I'm going crazy!!!!!
Thank you

Well I thought that what you we're looking for is 'Writing on the Wall' by Holly. At least it sounds a lot like it. but since you say it was the other one, I'll move this to 'found'.