Satarran
Satarrans are a humanoid race native to the Alpha Quadrant. They once attempted to manipulate the Federation into destroying their enemies -- the Lysians -- for them. They are an alien of the week from the TNG episode "Conundrum".
Attributes
Satarrans have the ability to look like other humanoids. Whether this is a natural ability or some kind of technology is unknown. They are resistant to phaser stuns: it took several hits to incapacitate their agent, "MacDuff".
Technology
The Satarrans have weapon technology comparable to the Lysians, which is known to be far behind that of the Federation in most fields, most notably weapon and shield technologies.
Oddly, the Satarrans (and possibly the Lysians) had access to extremely advanced computer and neuroscience technologies which they used to selectively erase the memories of both the USS Enterprise's computers and the ship's crew. Since being so far ahead of the Federation in these two fields while so far behind in many others is implausible, some have hypothesized that "MacDuff" employed advanced alien technology that he acquired somewhere for his ruse instead of Satarran technology.