Arrival and Departure
The Herd always arrives and departs in the proximity of That Which Changes
, at a distance between 135 and 145 million kilometers. They appear to use the duality of waves and particles to travel between this energy field and a comparable phenomenon in a different system.
The way they explained it to The Hive
, they simultaneously exist in both places during the rare moment when the electromagnetic frequencies are sufficiently aligned. Once this moment has passed, they are again limited to a physical form at their destination.
Travel within the System
A similar mechanism is used to speed up travel within The Star System. They mainly propel themselves forwards using an exothermic chemical reaction, traveling between locations where the electromagnetic waves overlap in a manner that allows the ships to jump from one to another.
These shortcuts let them cross the distance between celestial bodies far more efficiently than by their propulsion alone.
On average, they can travel about 406000 km per hour using this method.
Furthermore, they plan their travels depending on the orbital position of the celestial bodies. They mostly travel when the distances are minimal, shortening or extending their foraging stays as needed.
Once they arrive at a celestial body, they spread out over its surface and begin feeding on the available materials. These can include gases, liquids, minerals or plants.
Herd ships generally avoid consuming sentient beings, although accidental ingestion of smaller animals can happen. To reduce the risk of such accidents, herd ships have learned to emit subtle soundwaves which repel most creatures while they feed.
Herd ships can extract nutrition from most materials. Dead cells and metabolic waste products are excreted into the environment where they either serve as fertilizer for local plantlife or are slowly transformed by the radiation energies suffusing the visited system.
Said excretions also include chemically inert elements such as noble gases and precious metals, which gave rise to legends about finding great riches after the mysterious visits.
Between feeding sessions, herd ships tend to sit in illuminated areas where they can take in radiation. Some of that energy is used in the digestion process, kickstarting the necessary chemical reactions for breaking down the consumed matter. Most of it, however, is converted to chemical energy and stored for later use.