But the Lord of the Lashes says ‘Nay, nay, nay,'
We're gonna march all day, all day, all day,
Where there's a whip there's a way."
Royal heritage is no guarantee of success in Tolkien's world. The
Witch-king is reputed to be a royal Numenorean, and of course Sauron and
Saruman are Maiar. Boromir and Denethor are as royal as Faramir and
Prince Imrahil, and almost as royal as Aragorn. Lotho Sackville-Baggins
is Frodo's closest relative. Turin had the same heritage as Tuor.
In short, creeps and deeply flawed characters can come from any family.
The only real guarantee is that hope will survive, but that does not mean Frodo
and Aragorn will succeed now, as opposed to someone else succeeding
later. From the perspective of Eru, everything Aragorn did was
predictable, and predicted, but not from the perspective of Aragorn. The
biggest trap of prophecies is to rely on them, as the Witch-king learns.
Aragorn may have had an even tougher challenge because of all the
prophecies. He constantly had to turn away from or jeopardize his destiny
in order to make the prophecies come true. If he had once let ambition
rule his actions, he would have been in deep, deep trouble.
So yes, Aragorn was fated to be king, just as Frodo was fated to bear the Ring
to Mount Doom – but we can only say that for sure in hindsight, and for them at
the time the prophecies were as much a curse as a blessing.
Desperation may not be the word, but service to others is important. It
was Aragorn's concern for Frodo and Gondor that got him through the Paths, not
his own ambition to be king, and certainly not his own fear of death. And
as I said above, Aragorn could not be sure of anything, prophecies or no
prophecies. He took his chances, and it worked – barely! Remember
that he precipitated the very attack he was racing to counter by using the
palantir. If he had been truly desperate or afraid, he might never have
used the
palantir.
Morgoth personally was cast into the void beyond the walls of the world, not to return until the end of time. But he had infused so much of his personal power into the fabric of Middle-Earth that the whole place is more or less hot with evil radiation (he was particularly fond of gold, and hence it tends to be a special focus of evil). I find it very helpful to think of Morgoth's corruption of the earth in terms of radioactivity; there's a little bit of it everywhere (background Morgoth), and it can be concentrated and/or used as a power source.
Sauron no doubt employs the power of Morgoth routinely, and may have special access to it through Mt Doom (most of Morgoth's power, after all, went deep into the earth). He may have some way to commune with the spirit of Morgoth, although Morgoth is outside the world and technically dead.
The key thing to understand, though, is that Morgoth was a vastly greater power than Sauron. As Sauron's One Ring radiates temptation and corruption, because it hold the greater part of Sauron's power, so too does the fabric of the earth, the vessel of Morgoth's power, do the same thing; all the world is Morgoth's Ring. This means that we are constantly under assault from evil impulses, and our perceptions are under the Shadow (so, for instance, we may even find fault with the Valar's governance of the world!). In effect, the essence of Morgoth becomes an external cause of what theologians call the Depravity of Man.
Because of the corruption of all matter, Elves' bodies will not last forever, as intended. This is a problem for their souls, which WILL last forever. Hence, elves in Middle-Earth will eventually 'fade' into something very like a wraith. Apparently the Elven-Rings can hold this effect at bay over a limited area. This is what it means when Elrond says that they have great power to preserve all things unstained - they can exclude the Morgoth-taint, so that places like Rivendell and Lorien give us a glimpse of what Arda Unstained should have been like. The failure of the Elven-Rings after the War of the Ring is why all the Elves who could HAD to sail west; to avoid fading.
And that should hold you for now. -- Reverend's explanation of Morgoth's taint. R.I.P., Reverend.