Incutilis

Incutilises are intelligent, nautilus-like sea creatures that attack their victims' brains to take over their bodies, creating puppets to use for labor, combat, or their own malevolent amusement.

An adult incutilis is slightly smaller than an adult human head, and their shell bears a pattern of crimson streaks that resemble the ridges and furrows of a brain. Incutilises hatch within the depths of the sea, where they start off consuming bottom-dwelling crustaceans and sometimes even whales or sharks. As they grow into adults, incutilises instinctively crave the complex tissues of other creatures' brains—the more complex, the better—preferring to target humanoids and animals.

Eventually, an incutilis will make an excursion onto land specifically to find a puppet to control. Using their tentacles to crawl up onto shore or climb aboard a ship, they then drive their tendrils directly into the brain of a helpless living (or very recently dead) land creature. An incutilis takes control of their new host through this neurological connection. This host—now called a puppet—rarely survives the experience.

After an incutilis has taken full control, they can usually ride their puppet for as long as they wish. Often, they use the puppet to seek out other potential prey, battling other creatures until the wear and tear from repeated conflict renders their current body useless.