The sphinx is a hypocrite
Not only is he a hypocrite, he's a delusional, self assured, hypocrite.
"the best way to avoid being the slave is to be the master"
- The Sphinx, Keys to the Demon Prison
What I get from that is he's happy to enslave others, as long as he's the master.
"as master I will release the prisoners and create a world without slaves"
- The Sphinx, Keys to the Demon Prison
He says without slaves, but using the term master counters that.
The comments made about the different beings on the preserve also contradict it. He has the one being tied up and enslaved to him guarding the secret exit to the prison, he has the sphinx bound at the entrance to the fairy queens shrine.
He says preserves are bad, oh except when he's in charge, it's fine then.
His whole plan to *free* the demons seems less like he's trying to free them for real, and more like he's trying to create some sort of utopia, with him as the supreme ruler.
He's willing to turn away if the demons don't obey, is that not the same thing that the dragons faced to be put in preserves? They were defeated and their only choice was to be killed off or agree to the terms of their surrender.
It sounds like the sphinx is doing the same, the demons can stay imprisoned, or they can bow to him and swear themselves to what he wants.
He doesn't want the world destroyed, he wants to rule it. And he doesn't even really hide it.
He wants to be known, he wants a kingdom to leave behind, a legacy.
He's a filthy hypocrite that wants to rule and has twisted *morals* that he uses to justify what's really the slave turning around to be the master.
He admits to wanting to be the master.
Basically, he's a hypocrite that was fully prepared to enslave the demons under the guise of bringing world peace, you know, as long as he was in charge.