I have what is likely too many ideas for this particular series, so I thought I'd start with what I'm thinking about at the moment. I'd also like to offer a disclaimer - if you aren't interested in Tolkien, Middle-Earth, etc. at all, skip this. If you have not read The Hobbit, The Lord of the Rings and The Silmarillion at least by Tolkien, some of this will not make a lot of sense. I'm assuming some familiarity, but will try to explain things clearly so everyone will get something out of this series. Also, always know that I am simplifying what I talk about a great deal. Always assume that hundreds of pages are being condensed into a few paragraphs when I talk about Tolkien.
Life and death are central themes of all of Tolkien's works. The very nature of the world as it is created presents deep questions about life and death. The Elves, the First Children of Illuvatar (read: God) are immortal. They can only die by violence or by grief. Otherwise, they will live on forever at the peak of their power and vitality. Galadriel, for example, is over ten thousand years old when she appears in The Fellowship of the Ring - she was alive when there wasn't even a sun and moon yet, but the world was lit by the shining fruit of two sacred trees, and before by the stars alone.
Men, on the other hand, the Second Children of Illuvatar, die. They are fragile in every familliar way. In fact, death is described as Illuvatar's gift to Men - they alone of the conscious creatures inhabiting Middle-Earth are able to, through death, leave the confines of the world and travel...elsewhere. It is never said where they go, or how they arrive there, or what happens next. Tolkien leaves mortality a great mystery, which is one of the things I appreciate about mythopoetical work.
In the portion of the Silmarillion called the Akallabeth, this question of death and immortality is brought to a head. There has arisen a race of Men called the Numenoreans. They are the peak of human capacity in every way - in warfare, in craft, in exploration, in intelligence, etc. They are granted an island to live upon, and continue to develop their advanced civilization there.
Over time, however, they come to love their lives too much. They seek ways to live longer and longer, and they begin to fear death and nothing else. They build massive tombs and learn to preserve bodies and are always motivated by the fear of their own mortality.
This fear becomes so acute that the Numenoreans come under the influence of Sauron (yes, the Dark Lord from the Lord of the Rings). Sauron knows he can't overcome them openly - they're too powerful - so he corrupts them from within. He plays on their fear of their own mortality, and in the space of a few generations he is able to convince them to sail West to the Undying Lands and wrest eternal life from the Valar (who are essentially powerful angels or servant-gods of Illuvatar).
So a few faithful Numenoreans sail East to Middle-Earth (Aragorn is a distant desecendent of these) and many sail West to challenge the gods and escape their mortality. The result is the downfall of Numenor. For their hubris, the Numenoreans are thrown down and their island is devoured by the earth and covered by the sea, their civilization wiped out forever.
Now, what does this say to me theologically? That eternal life should be something other than the understandable, but selfish and unnatural, desire to prolong my own life as I know it now. That grasping is rooted in a fear of death, and death is part of life, as trite as that sounds. It is rooted in the desire to be strong, to be young, forever, rather than to succumb to time and age, to nature and mortality.
It also says a great deal about trust. What happens when mortals die is not dealt with in Tolkien's writing - it is only said that they depart, and that no one, not even the Elves or the Valar, know where they go. This is Illuvatar's design from the beginning - that death be a final mystery.
Could we say that death was part of God's design from the beginning? Scripturally, I think it is justifiable. Death is depicted as entering creation through the Garden of Eden, but a creation that remains in Eden is hardly a creation at all. When God allows choice, then drama arises on a cosmic scale. When God makes creation free, even in part, then there is jeopardy and triumph, gain and loss, sin and repentance. When God allows the chance of death, then I think God allows a chance at meaningful life as well.
Is death then an evil? In faith we affirm that it is not an ending, but like the Numenoreans, like every being conscious of its own mortality, we can't be sure what comes after. Like Tolkien, I'm not motivated to get into the details of what I think comes next. For me, the challenge is in coming to see it as a gift rather than a curse, as something to be accepted rather than feared and hated. It is hard to learn to let go.