The Sky Whales are the biggest flying life forms of Blue Moon, reaching 5.25 meters in body length and supported by a 10 meters wingspan. Although they weigh up to 800 kg, they're able to float through the sky because the atmosphere of Blue Moon is much thicker than Earth's atmosphere. These grazers spend their entire life on the wing eating small algae living in the sky of the planet. Their only predator are swarms of Caped Stalkers who are able to kill them because of their majority. They can evade their predators by flying upwards in a spiral pattern, then by diving to be carried by Blue Moon's strong thermal currents.
According to concept art, the sacs on the back of the Sky Whale's head are vocal organs located above the animal's lungs. They inflate slightly as slits behind them open which then emits a sound. Additionally, they depend on echolocation and acute hearing to detect their surroundings as they are blind. The bone structure of their wings have a hexagonal structure which provides great durability.