Remember after Yuber gets beaten in S3
He says "Will my pain ever end"
I think he has a cursed rune much like the Soul Eater, Rune of Punishment...
And it holds sway over demons much like the Dragon runes allows dragons to exist.
The rune craves blood and chaos (Like the beast rune)
Perhaps Pesmerga is Yuber's clone or vice versa
Luc and Sasarai are Hikusaak's clone.
I suppose if I had to guess....Id say Yuber and Pesmerga were guardians of the true rune and Yuber stole it...thus Pesmerga follows him to get it back.
"All that we see or seem is but a dream within a dream"