Corio's face will go completely white as he ages. The muzzle spots are a symbol of his downfall (being shown before the snap). The snake on his shoulder is just a tie-in to him being a snake. He is also a Saluki :3 cause it was a nobles breed.

Sejanus is an airedale terrier. His fur lightens as he ages (a trait of an airedale). He has a heart on both wrists "wears his heart on his sleeve" deal. His markings on his neck are a symbol of his death.

Thank you!!