Ginormous space creatures with planet-sized explorable environments on their backs. Some variants may be dead versions, existing as shells or giant skeletons.
These may be inspired by: Turtles, Tardigrades, Whales, Axolotls, Sharks, Shrimps, etc.
Fauna are typically far more abundant on these living planets than on any other type. They make great homes for zoos and cooking operations.