Daphne is one of the Witches of Sin, being the Witch of Gluttony. All she wants is to be full, it's her reason for living. Daphne enjoys giving people nicknames, such as Subarun for Subaru.
Spoiler Daphne's main ability is "Authority of Gluttony". With this authority, Daphne is able to cause a individual to have and feel extreme levels of hunger by just touching them or looking at them. When Subaru encountered Daphne it only look one look from her left eye for him to start eating his arm and ignores everything that was going on around him. Echidna states that a look from Daphne's left eye isn't all impressive and the true terror of Daphne comes when she uses her right eye or eats her target.