Could Valtiel be responsible for ALL monster manifestations?He "recycles" living beings, monsters, or whatever that dies in the Otherworld. He resurrects even Heather.
Sure, Samael/God is a powerfull being that lives in the Otherworld, but I don't think the entire Otherworld is HIS domain. The Otherworld is a living, and not necissarily 'evil' entity of it's own, that both manifests strong human emotions, AND is home to some powerfull otherworldly beings like God (assuming God is not just a manifestation).
Therefore, I don't think an agent of God could have such a high responsibility as to rebirth all poor souls that are lost in the Otherworld.
Possibly, he only rebirths those souls that may help in the process of birthing God.
Am I making any sense?