Balloon Jellies are large creatures native to the End, floating in the empty 'void oceans' between islands and preying on tiny flying organisms including their own young. They have a hollow body filled with light gases that allow them to float, with spiracles on the sides of their body for gas exchange to let them change the height at which they fly. They have many tendrils that they use to filter-feed, eating small lifeforms as mentioned before. Porous obsidian shells hold their bodies together, providing structure while keeping them somewhat lightweight.