Decadrons are insect-like creatures native to any planet containing water or other similar forms of liquid. On Earth, they are typically found feeding on the surfaces of whales, a process known as mutalism, much like birds and large African mammals do. They are relatively small, about the size of shrimp and eat smaller organisms, like plankton and krill.
Decadrons often travel in groups, some large, some small depending on the situation. Member of these groups clean and groom each other and tend to their helpless young. Amongst these groups, there is typically a queen, which is covered in spikes giving it the appearance of a sea urchin. It uses these spikes as protection.
The young (also known as "nymphs", though the reason of the given name is unknown) surround the queen, while the other adults surround the "nymphs". The "nymphs" will also cling to the queen's spikes as for protection. Some of the adults are known to go cannibal on the young, but the queen usually drives them out of the group if this happens. If the group is large enough, they may be able to skeletonize fish.