Power, organization, masculinity are the focus of the Emperor card. He is also the strongest father archetype in the Tarot.

He holds in his right hand a sceptre. It represents his ability to direct the forces of nature. A mirrored metallic orb passes over his left hand. It symbolizes his dependence on the earth as the base for his ambitious projects.

His limbs and torso draw the number four with the numerological meaning of stability that also reflects the order of his card in the Tarot.
The Emperor is the organizing and governing principle within each of us

Of course I thought about James for this card, but actually Sirius is a better father figure for Harry than James...