Emperor Mollusk Versus The Sinister Brain by A. Lee Martinez
Emperor Mollusk.
Intergalactic Menace. Destroyer of Worlds. Conqueror of Other Worlds. Mad Genius. Ex-Warlord of Earth.
Not bad for a guy without a spine.
But what's a villain to do after he's done . . . everything. With no new ambitions, he's happy to pitch in and solve the energy crisis or repel aliens invaders should the need arise, but if he had his way, he'd prefer to be left alone to explore the boundaries of dangerous science. Just as a hobby, of course.
Retirement isn't easy though. If the boredom doesn't get him, there's always the Venusians. Or the Saturnites. Or the Mercurials. Or . . . well, you get the idea. If that wasn't bad enough, there's also the assassins of a legendary death cult and an up-and-coming megalomaniac (as brilliant as he is bodiless) who have marked Emperor for their own nefarious purposes. But Mollusk isn't about to let the Earth slip out of his own tentacles and into the less capable clutches of another. So it's time to dust off the old death ray and come out of retirement. Except this time, he's not out to rule the world. He's out to save it from the peril of THE SINISTER BRAIN!