Cytoplasts are small masses of living tissue, magical in nature, appearing as blue-green globules. These globules convey genetic information to and from any life-form they come into physical contact with. For example, if a cytoplast in contact with a giant is transferred to a human, the cytoplast then begins to incorporate into the human the physical strength of the giant. Cytoplasts also tend take on the physical characteristics of their hosts somewhat camouflaging themselves.
Unfortunately for Vig, the people of Ravnica did not want to be improved or to undergo the surgery required to receive the benefits (except Simic members and people requiring prosthetics), so Vig created a new version of cytoplast that only need to come into contact with a host in order to bond with it. This allowed Vig to improve the people of Ravnica without needing their consent.