Infector

In appearance, Infectors look like headless bats made from dead human material. The strange winged Infector acts as the fastest vector for the contagion, only attacking or defending itself when it cannot find any hosts to infect.

Apparently created from human torsos and arms, its wings are formed by a flap of skin flayed away from the flanks and chest and then fused between the former host's twisted arms. The head appears to either be missing or consumed, and the pelvis is the new "head" of the creature, with the spine providing support and attachment points for articulation (movement). All non-essential musculature, fat, and organs have been removed, owing to its bony appearance along the back. This biomass is likely used to produce the infectious agent the creature administers with its proboscis. This limb, made from mutated bone, muscle, and spinal tissue is the delivery mechanism used to infect potential hosts. This is done by enveloping the host in its wings, extending the proboscis from the spinal cavity, and then stabbing it into the skull to inject a yellow fluid stored in an internal bladder. In any room with the remains of crew members, these are the beasts that should be taken down quickly before you get overrun with newly created Necromorphs.

They seem to have a preference for corpses which have existing head wounds, possibly because this spares them having to crack the skull themselves