Dutiful and serious, Marx is often frustrated by the Magic Emperor's tendency to shirk his duties and go off searching for new magic. He frequently loses his composure when dealing with Julius's starry-eyed outbursts about various magic, and struggles to keep the Emperor on task. Though a high-ranked mage who works alongside Clover's top officials, Marx has an amiable and courteous personality as shown when he treats Asta with respect despite his low status. 

Marx Voice Actor: Aaron Dismuke

Reference: Couldn't find one. So this role will be up to interpretation!