Mufasa

 Mufasa is Simba's father, and thus Kion's grandfather. He has been confirmed as a character that will be appearing in The Lion Guard, albeit as a spiritual guide for Kion.

Appearance
Mufasa's appearance in The Lion Guard has not yet been announced. It is possible that he is amongst the elders in the clouds as seen in many promotional shots.

Personality
In the original movie, The Lion King, Mufasa is shown to be a fearless leader. It is unknown at this time what his personality will be like in The Lion Guard.