It is said that if even one of their hairs is plucked, the Vila will die, or be forced to change back to her true shape. A human may gain the control of a vila by stealing a piece of the vila's skin. Once burned, though, she will disappear.
"The voices of the Vilas are as beautiful as the rest of them, and can form large gusts of winds that can lift houses into the air. Despite their feminine charms, however, the Vila are fierce warriors. The earth is said to shake when they do battle. They have healing and prophetic powers and are sometimes willing to help human beings. At other times, they lure young men to dance with them, which according to their mood can be a very good or very bad thing for the man. They will kill any man who defies them or breaks his word. Vila rings of deep thick grass are left where they have danced; these should never be trodden upon, as this brings bad luck." -Wikipedia