What is the prenomen or royal name of the ancient ruler of Egypt and a kingdom at the confluences of the Blue Nile, White Nile, and River Atbara?
Tantamani:  His prenomen or royal name was Bakare which means "Glorious is the Soul of Re." Kingdom of Kush: The Kingdom of Kush or Kush ( ) was an ancient kingdom in Nubia, located at the confluences of the Blue Nile, White Nile and River Atbara in what is now Sudan and South Sudan.
Bakare