You're probably thinking of Elder Evils (Dec. 2007) that contains several cosmic big bads (although not all can be described as Lovecraftian), the big bads' minions, and their plots that see them trying to alter or destroy the worlds. It includes rules for, for example, signs of the coming apocalypses that telegraph their arrival.
For example, the book summarizes chapter 2 about Atropus as follows:
This moonlike orb is the stillborn afterbirth of the world’s creation, an undead entity that desires nothing less than the end of the entire multiverse. (4)
And, for example, the book summarizes chapter 7 about Ragnorra as follows:
Arising in a time before creation, Ragnorra is a force of perverted life that births monstrosities from her swollen body. The deities cast her into the sky, but she reappears as a blood-red comet every 500 years. Dreadful seed and falling stars produce monstrous offspring in worlds Ragnorra approaches—and now she smashes into worlds to remake them directly. (ibid.)
Unlike the similarly titled Exemplars of Evil (Sept. 2007), there's little for players in Elder Evils so it's not often mentioned in discussions of, for instance, character-building.