Vendorian

Vendorian shapeshifter in its natural form.

The Vendorians are a shapeshifting non-humanoid species that are capable of manifesting themselves into anything of similar size and mass. While Vendorians may assume many shapes and identities, the longer they remain in one form the more characteristics of that form they assume. This is particularly true when a Vendorian assumes a humanoid form. In these instances the Vendorian absorbs memories and personality traits of an individual through touch. These memories and traits become more ingrained the longer or more frequently the Vendorian assumes the form; if maintained long enough the absorbed traits eventually become part of the Vendorian's own personality.

Vendorians also have the ability to render some humanoids, particularly Humans, unconscious by touch alone.

It is unknown whether this process is chemical/electrical or mechanical, such as the Vulcan nerve pinch. Though it was demonstrated several times on-screen an explanation was never provided.

Due to the Vendorian's deceitful way of life, the Federation imposed a quarantine on their homeworld, Vendor, declaring it as off-limits.

As a stipulation of the treaty between the Federation and Romulan Empire, use of Vendorian spies is considered a violation of said treaty. (TAS: "The Survivor")

It is unknown if this refers to the treaty established following the Earth-Romulan War of 2161, or the more recent Neutral Zone Treaty.

Virtual Enterprise, a non canon, script-format, fan written continuation of Star Trek: Enterprise, mentions the Vendorians in their eighth episodes, "Right Wing."