When the Overlord is subjected to the Overseer strain mutation, its eyes melt into a luminescent substance that floats inside a semi-transparent skull. Sensory tentacles and twin photoreceptors—capable of sight in any environment—sprout from said substance, in between the openings of their thick, armored “faceplate”. To further enhance the creature’s capabilities, the main body expands and grows six new hypersensitive optical receptors in strategic positions—ensuring that not even cloaked threats escape the Overseer.
Evolution is a curious thing. The first batch of Overseers ended up crippled and blind when the arrays of microscopic filaments—relays of sensory and spatial data—located on their vestigial legs gained sentience and became ravenous to the point of consuming the appendages that housed them. To correct this situation, the legs were excised and the filaments were transformed into long, fleshy tendrils grown from the Overseer’s carapace.
By incorporating Terran DNA into the Overseer’s genetic makeup—particularly during its later stages of pupation—the creature displays a peculiar evolution pattern. Its creep glands expand and turn into stores of sentient, unfertilized bio-matter, and its organs no longer liquefy into creep, but instead a nourishing paste. At the Overseer’s will, this paste bonds with the bio-matter in the sacs and quickly becomes an insidious infiltrator known as the Changeling
The sentient, unfertilized bio-matter that resides within the Overseer grows and solidifies at exponential rates when exposed to foreign atmospheres. The Swarm has capitalized on this trait, using its Overseers to disable critical facilities in the midst of an invasion.