The Right Stars
Summary: Cthulhu never imagined saving the world, instead of destroying it.
Cthulhu slept in dread R'lyeh, beyond death and dreaming as mortals knew them. As his mind drifted across the Dreamlands, a mighty thud impacted his transdimensional sanctuary. Still recovering from a ship to the gut, Cthulhu stirred before opening the hypergeometric portal to his realm. Outside, Cthulhu met the foe he never knew he had.
Cthulhu was intimately familiar with rival Great Old Ones and Elder Gods, like Shub-Niggurath, Hastur, and Nyarlathotep. Cthulhu was familiar with humanity, with their fragile minds and feeble machines. Cthulhu was aware of the races that preceded humanity, like the Elder Things of Antarctica, the Great Race of Yith, the opportunistic Deep Ones, the cloying serpent men, his own star spawn, and the Deep Ones that worshipped him under a thousand names. The foe that awaited him was none of them.
Cthulhu emerged to hear a cacophonic song resounding through the world's waves. Hordes of psychic beings merged their awareness into a single entity, a horrid hivemind. The component beings were ones even the humans dismissed, the simple cetaceans known as dolphins. Somehow, they'd awakened their latent psychic powers, and they became aware of his existence. They were attacking him on multiple dimensions at once, a feat even the mightiest humans were incapable of.
Cthulhu grappled with the dolphinic hivemind across several planes and epochs, as they stepped in and out of time to battle him. As he gathered his own servitors, they gathered resisting humans and fought back. Their strikes were superficial and shallow, but they served to distract the cruel, alien consciousness. With the momentary distraction, Cthulhu cast it apart with decisive celerity.
Cthulhu staggered back, as he was not at full strength. The battle had drained him of what strength he recovered. His own recovery would come once more, when the stars were right once more. In that time, he hoped the de-evolved dolphins would not attempt such an assault again. It was due to their alarming alacrity that their attack made it as far as it did. He ordered his cultists to prevent such an event from happening again.
Cthulhu awoke an eon later, when the stars were finally right. He emerged from his risen city to find a flotilla of ships and aircraft, human vehicles gathered by Deep Ones and star spawn. His cultists then connected their master to their machine, and Cthulhu realized what they'd been up to in the interim ages. This time, he was pleasantly surprised.
By defeating the dolphin overlords, Cthulhu's cult were seen as saviors by humanity. Generations of human children grew up with beloved Cthulhu plush toys. After reverse engineering the method of dolphin telepathy, the Deep Ones merged their magic with human technology. They'd established a hive-mind of their own, which their overlord would directly command. In that way, Cthulhu's awakening happened under the right stars. Instead of being an era of madness, it was the start of the golden age.