Marcus

Marcus is one of three vampires in Italy who live what Edward described as a very civilized and educated lifestyle. Carlisle found them while on his own search for the truth behind his nature. The Italian vampires tried to cure Carlisle of “his aversion to his natural food source,” but they failed. Their likeness was depicted in several painting by Solimena.

History
As a result of losing his mate - Didyme - Marcus eventually became extremely apathetic. He voted against destroying Renesmee in an 'almost bored fashion', not even looking at the Cullens and their allies while doing so. The others of the Volturi seem to recognize this aspect of himself, as none of the Volturi reacted at all to his vote.

Relationship
Marcus lost his mate, Didyme when her brother Aro killed her. He never knew Aro killed her. That loss, over the centuries, turned him into the apathetic zombie he is today.

Talent
Marcus has the ablility to recognize relationships. Stephenie Meyer described Marcus's powers as the following:

"Marcus’s gift is actually quite valuable in the hands of someone who knows how to use it. For example, imagine Marcus on the battle field. He sees the binding ties between the enemy the guard faces. He can tell who the leader is just by watching the way the others are tied to him or her. He can see how to destroy the resistance simply by picking off a few key people. He doesn’t just see romantic relationships, but also ties of family and friends, loyalty and devotion. He can tell if any given person would die for another. Off the field of battle (as the Volturi rarely leave their home), Marcus’s gift is valuable politically (for lack of a better word). It’s an amazing gift in a diplomatic situation. Plus, when you’re sitting on an empire, it’s nice to be able to see when someone’s loyalty starts wavering. Or if anyone is getting too fond of anyone else. Can you see the potential now? Marcus didn’t get where he is with some fluff skill."

When Marcus first encounters Bella and Edward, he is surprised by the intensity of their relationship. He shares this information with Aro mentally and never utters a single word.

Actor Portrayal
Christopher Heyerdahl will be playing the character Marcus in the upcoming film, New Moon.