What is insanity? We find ourselves asking this question, trying to find the right definition and explanation for others who act out of the ordinary.

King Ferdinand... was a kind man, although he was stubborn at times, he meant well...... whatever this is... it is NOT Ferdinand. Some entity has taken over his corpse and uses him as a false avatar, an incomplete puppet. He is INSANE. He has reason to do things but how he goes about his path is chaotic, unpredictable, and unstable. He has a set plan, but as to what this plan is, he dances around with insane ramblings that lead no where. He goes from 0 to 100 in an instant, no off switch whatsoever. 

His voice has a couple of very specific references, and I ask that you try to mimic it to the best of your ability.

This is a reference to his inflections and how he speaks. He has a deep bassy voice but shoots to highs and lows and screams and hits a note in the middle of his words. Like he cant contain the music within him. Think of it like Joker's Laugh in the Joker Movie, its a painful inflection where he just does it out of forced habit. (Hard to explain without listening to the video)
Peter Maxwell Davies - Eight Songs for a Mad King for Baritone and Ensemble (1969) [Score-Video]

2nd reference which is similar to the 1st. (Its the 2nd guy) Where its just a broken mind- trying to formulate sentences. In the middle of him talking, have him lose his words like his mind is just fucking GONE. Not of this earth, before he pulls himself back and speaks like reference 1.
https://www.youtube.com/watch?v=4GREPjrPJkk&pp=ygUYc2hhZG93IG9mIHdhciBicm9rZW4gb3Jj

This role specifically allows for a lot of improv. Even though the lines or audition may say something, feel free to deviate if you think it works!