[Nils]

I would call The Halls of Mandos an "Elven Purgatory". Manwe could delay the restoration "if the fea while alive had done evil deeds and refused to repent of them, or still harboured any malice aginst any other person among the living."*

*From the second Glorfindel Essay in "The Peoples of Middle Earth".

Kuruharan,

I believe Eru's gift was Man's soul was not bound to Arda. Even Elves died, but only men could pass through the Halls.