Mandos - The Halls of Waiting.

[Mhoram]

I agree with you zif,

“…and he (Melkor) was cast into prison in the fastness of Mandos, whence none can escape, neither Vala, nor Elf, nor mortal Man.”

This was done with the thought that Melkor might be rehabilitated, as we can conclude by the fact that he had a parole board hearing 3 ages later and Manwe believed that he was indeed rehabiliated.

If they thought that Melkor could be rehabilitated, then surely they give the same chance to the other Maiar that die after a life of evil.

I wouldn't put overmuch value in the accounts of Saruman and Sauron's spirit/mists after their deaths, this was afterall part of the Lord of the Rings, before Tolkien had figured out how everything worked with spirits and such.

I have no text to present, but I would assume both Saruman and Sauron were summoned to the Halls of Mandos. Whether or not spirits can deny the summons, that's a question that needs to be tackled. It seems Sauron did after his body was destroyed in the fall of Numenor. I know i've read somewhere in a thread about elves denying the summons, if someone could present that text, it would help.