Shapeshifters from Vendor whose talent for deception made them useful to the Romulans, who used one to impersonate Carter Winston.
The Vendorians are shapeshifters from the planet Vendor, able to rearrange their molecular structure to take on the appearance of other beings or objects. Their natural form is multi-limbed, and they are viewed with suspicion because of their skill at deception.
In The Survivor, a Vendorian working for the Romulans impersonated Carter Winston, a long-missing philanthropist, and came aboard the Enterprise to sabotage it near the Romulan Neutral Zone. Its plan unravelled after it came to share Winston's feelings for his fiancee, Lieutenant Anne Nored, and it ultimately helped the crew.