Reading the Lord of the Rings makes for some thoughtful moments, as to what is _behind_ the comments of characters like Gandalf, Elrond, Galadriel, et al. This lead me - along with some confusion about Middle Earth geography - to my old copy of Fonstad's "The Atlas of Middle Earth". In addition to the atlas aspect, there is a summary of events in Tolkein's legendary history.
On p.1 she summarizes "Iluvatar sent the Valar to order the world, preparing Arda for the coming of his Children - Elves and Men. Melkor, brother of Manwe, being arrogant in his own strength and power sought to mar all the works of the other Vala. Thus, Arda began in battle and turmoil: the Valar, building; Melkor, destroying."
Oddly, above this opening sequence about the nature of strife in Middle Earth, she quotes Genesis 1:1 "In the beginning..." Aside from it being a creation story, I'm uncertain what prompted Fonstad to make the Genesis reference although there are some similarities between Tolkein's mythology and the story of God's creation. In any event, the strife of the Elder Days is attributed to the arrogance and destructiveness of one of the lesser gods. Sauron, it may be remembered, is a lieutenant of Melkor [aka Morgoth].
The Wiki reference says this about Melkor:
This explanation seems to pit Melkor against his maker. The feeling I get is that Tolkein attributes the strife of middle earth to the strife of the "lesser gods", or the strife between them, perhaps. These lesser gods act upon creation and pursue their ends in it which sometimes clash out of purposeful intent, similar to the Greco-Roman pantheon of pagan gods. They also have freedom to create, act, interfere, etc., in a very open way, raising or leveling mountains, besieging Melkor's fortress, fighting battles openly, etc. Literally, Tolkein's gods walk the earth and fight openly.
There's more responsibility put upon us, God's children, then Iluvatar's children - elves and men, for the evil in the world. Satan certainly pursues lies and murder as his trade. Jesus says the devil "...was a murderer from the beginning, not holding to the truth, for there is no truth in him. When he lies, he speaks his native language, for his is a liar and the father of lies." [Jn 8:44]. Yet it is Eve, and Adam, who disobey God's command not to eat from the tree of the knowledge of good and evil, albeit swayed by "the serpent" and his arguments, that bring about the fall. The devil doesn't appear and destroy the tree, oppress the children, and wage war openly and in bloody medieval fashion! Satan fights his war across the spiritual realm of humanity's souls.
Of this world, Jesus says, "This is the verdict: Light has come into the world, but men loved darkness instead of light because their deeds were evil. Everyone who does evil hates the light, and will not come into the light for fear that his deeds will be exposed. But whoever lives by the truth comes into the light, so that it may be seen plainly that what he has done has been done through God." [Jn 3:19-21].While the fallen angel and his minions do battle against God, humans have the responsibility to live by the truth and come into the light, revealing truth lived through God. Here we are not just victims of violent gods and their battles - we are the responsible party in the struggle for and against God.
The John quote also gives good insight as to why Sauron and all the evil-doers love to work in darkness. They do not want to step into the light that illuminates and exposes their deeds for the evil that they are. There are so many darkness descriptions in LOTR that they can't be covered here.
Someone, somewhere, has certainly made detailed analysis of the theology of Tolkein's pagan / Saxon / mythological world. While I can't present such depth to you, it is always interesting to see how a pursuit like gaming [and movie-watching now] can be thought-provoking about the creation in which we live.