What was this official D & D 3.5e regulation with Lovecraft flavor?

I hardly remember a D & D 3.5 book, but I really can not remember its title. The book had a Lovecraftian flavor, it was official and it was about ancient gods and monsters that existed in the background, and the DM could create complete campaigns about them.

In general, he proposed that events occur in the campaign, and players had to find ways to divert the arrival / awakening of the big bad guys.

Does anyone happen to know the title of the book?