Keres Pronunciation: https://youtu.be/s5yAYawChlQ

Technically, Keres only appears in this season as a ghost, though he will likely make non-dead appearances in the future.

Keres is the former king of the Savannah Monarchy to which he ruled with an iron fist, he attempted to conquer the other lands of the Animal Kingdom until he was stopped and struck down by the original defenders. He appears now as an unleashed ghost in the present, seeking revenge for his downfall.

I imagine his voice sounding low, haunting, and sinister.