According to the description of Scepter of Shibaxet (The weapon of the Kind of the Wind Demons, Pazuzu) a demon lord can be redeemed
The Scepter of Shibaxet can be broken by a redeemed demon lord if the regenerating towers of Shibaxet are already destroyed.
The towers are his rookery, and can be found in his Abyssal plane.
But what happens after a demon lord is redeemed? Do they become gods or do they stay as demons or does something else altogether occur?