Here's why it's important to note:
* The Volturi are a powerful vampire coven: The Volturi are a powerful vampire coven that rules over all vampires. Marcus is a member of this coven.
* Marcus's power is "emotional empathy": In the *Twilight* saga, Marcus has the ability to sense emotions. He can feel the emotions of others and see their past experiences, like a memory flash. He doesn't have any physical powers, but his power of empathy makes him very valuable to the Volturi.
However, in *New Moon*, Marcus doesn't play a major role and his power is not emphasized.
Let me know if you have any other questions about the *Twilight* saga.