Though the exact fate of species captured by the Collectors is unclear, the humanoid appearance of the scions gives ghastly clues. The scion's frame and and skull are similar to those of a human or asari, but the bone structure is overlaid with a metallic resin. Posthumous examination of their bodies reveals a skin tone resembling that of Reaper husks, but their transformation process seems more extensive. Like husks, they are cybernetically modified on a nano-scale so they can operate any in hard vacuum. Hoses rather than veins and muscle tissue join major portions of the body together. One arm is replaced with a construct that fits a large rifle, turning the creature into a humanoid weapons platform, and a fleshy sack is supported by the creature's back and head.
These sacks contain brain matter and spinal tissue, too much to have come from just one victim. This indicates scions are an amalgam of several individuals, with one primary victim providing the frame and several "secondaries" providing the flesh for a decentralized semi-mechanical nervous system. This decentralization makes them highly resistant to gunshot wounds; even a headshot is not a certain kill.
The scions' weapons, however, indicate that scions retain some living tissue, or at least sustain some of the same electrochemical reactions as those of a human biotic. The weapon creates a powerful warp effect, which is consistent with the eezo nodules visible in the scion's expansive nervous system. Given the rarity of human biotics, it seems likely that these dust-form eezo nodules are deposited during their transformation, rather than requiring a biotic victim in the first place.