First off, there is no need for Contagonists to WANT to tempt or deflect the protagonist or others, it is just what they do. In other words, intent is not needed for a Contagonist to function (the same is pretty much true for all objective characters in the overall story).
The simplest example of a Contagonist I can think of is the little devil that sits on someone's shoulder giving them all sorts of bad advice. Of course, he is balanced out by the Guardian angel. It's important to note that a Contagonist represents temptation and hinder, but is not necessarily applied in any specific direction. The Story Goal gives a useful barometer for an author to use, but that not required for the character to do his job. In Star Wars, Darth Vader is the Contagonist. He deflects the efforts of the protagonist Luke by killing Obi-wan, but also deflects the antagonists' efforts by squabbling with Empire officers, and even suggesting that Gran Mof Tarkin let Luke et al leave the Death Star with the tracking device, which allows the rebels to find and exploit the Death Star's weakness before the Empire blows the Rebel's base to bits. Darth also represents temptation, as in 'here's what happens to you if you give into the temptation of the dark side of the Force.' In subsequent films, he more actively tempts Luke to join him.
The Contagonist need not be blurry, but may appear to be less obvious if it's functions are shown using subtle storytelling techniques.