Hector

Hector is the Warlock of Melancholy. Back in the era of the Witches, Hector was in pursuit of the Witch of Greed Echidna. Upon locating her in the Sanctuary, he swiftly defeated her apprentice Roswaal A Mathers and engaged in combat with the Witch though the outcome is unknown.

Strangely, his name was never recorded in history.

(Source: Re:Zero Wiki)