How might Morgoth go about escaping from the void?
I'm starting an RM campaign in Middle Earth and am contemplating having it culminate with the party teaming up with Sauron to prevent that from happening. Sauron, in the millenia since Morgoth's defeat, has changed goals. He's no longer looking to destroy Arda alongside his former master. He wants to rule it. If Morgoth returns he won't be able to because the prophecy of Dagor Daloroth may come to fruition and kick evils' ass for good.
It's set around T.A. 1440 with the Great Plague being the first sign of the barrier weakening. Sauron, in his guise as the Necromancer, is actively struggling against Morgoth. He, being who he is, isn't exactly doing it in a way that most people would consider "good."
PCs start off working against the Dark Religion, the Dark Mage of Rhudar, and other baddies who seem to have formed an alliance. Towards the end they learn that Sauron is waking and that there is a way to stop it. (insert something here).
When they get there, Sauron curses them for fools and shows them the truth of Morgoth's fingers reaching out of the void. They team up to stop whatever is causing it.
Yeah, there's a ton of work that needs to go into it to get from point A to point Z. Not the least of which is dropping enough clues along the way that the players have reason to believe Sauron at the penultimate point in the campaign.
Step one: how does Morgoth try to get out?
