A nightmare tide rises.
Flood infection forms are nightmarish homunculi spawned in massive numbers for the singular purpose of converting all living creatures into carriers, tools, and food for the parasite. The most commonly encountered infection forms have soft, pod-like bodies with numerous tentacle-like appendages and a frond-like array which acts as the creature's sensory system. Their tendrils are multi-purpose locomotion systems and insidious methods of control.
Each tendril ends in nano-scale barbs which can latch onto the target's body and cut through armor or environmental suits. Once the target is compromised, infection forms inject Flood cells to hijack the victim's nervous system. Even if the infection form is quickly removed, Flood cells in the wounds will slowly consume the victim and turn them into quivering, spore-packed blisters. Against unprepared victims the infection form bores into the body, quickly mutating it into a combat form.
Though barely intelligent on their own, once an infection form infiltrates a sentient creature they turn the victim's cognitive power to the furtherance of Flood goals. Each is an insidious puppeteer, able to sift through memories of any sentient creature to learn of military countermeasures, security access codes, and the location of population centers. This information is then shared with other Flood through their connection with the key minds.