Hulder are engineered for survival in the Titanian wilds. In silhouette, their bodies resemble a longlegged great auk, though viewed up close, the resemblance to a bird ends. Hulder have no feathers, but rather smooth, rubbery charcoal or black skin covering a thick layer of nano-augmented blubber. What resembles a thick bill from a distance is actually a seamless protrusion of the face, packed with sensory augmentations. Hulder stand 2 meters tall and weigh on average 135 kilograms. Their sensory organs, webbed feet, and fingers are all cybernetic.

Hulder can only tolerate temperatures hospitable to baseline transhumans for short periods of time. In the open, they must balance their bodies' chemical reservoirs with other hulder and caribou once per month or with a chemical reserve pack. A typical band of 2-6 hulder and 10-20 caribou can go about a year before having to visit a hab or a station like Huvudskär to replenish chemical reserves.