A mimetic simbiot was a clone created by a Lyssarian Desert Larvae that has been injected with DNA from another organism. Simbiots were identical to the original genetic donor, except that they underwent their entire life cycle in only fifteen days. The Lyssarian Prime Conclave banned the creation of simbiots, due to the ethical ramifications of creating living, sentient beings. This dictate was defied by the Velandran Circle, a group of Lyssarian scientists, whose illegal research on simbiots also led them to make largely unsubstantiated claims of a way to stop the rapid aging process.
In 2153, Doctor Phlox created a mimetic simbiot, named "Sim", of Charles Tucker III to serve as a tissue donor, after the real Tucker was injured in an engineering accident. Phlox subsequently discovered that simbiots based on Human DNA are significantly less resilient than simbiots based on Lyssarian DNA, being less able to cope with removal of brain tissue. (ENT: "Similitude")