[Bêthberry]

I think you might be on to something, Lalaith in asking which 'model' of deity is suggested here.

We have Tolkien's statement that he tried "consciously so in the revision" to suggest a Christian ethos and symbolism for his Legendarium. However, in also harkening back to the old Norse mythologies, he would find a different concept of deity--or certainly different deities who behaved with wilful abandon, excess, selfishness and selfcentredness, in short, with all the shortsightedness and lack of self control which humans possess. Are the tendencies of deities in the old heroic epics to be found in the Legendarium?

One other point, although Estelyn's dictionary definition suggests elements in sadism, it is incomplete in that it omits the dynamic nature of the tendency. Usually there is a willing partner, the masochist, who allows or submits to the game willingly. Sadism is not, simply, imposed cruelty but a dynamic relationship.

But another way to look at the question:

Does Eru play upon the emotional weaknesses of the people of Middle-earth? Are they free to control their proclivities so that they cannot be blindsided by him? Or surprised by the consequences of their own failings? Usually, in mythologies, it is the the secondary agent who is used to test and challenge the characters, not the main deity.

In Chrisitanity, that secondary agent is Satan, who has been understood in many different ways over the last four thousand centuries. He was not always the "grand and malevolent" figure, the great antagonist which Milton characterised in Paradise Lost but merely someone, an angel, sent to block or obstruct human activity in such a way as to teach people something about their own weaknesses and foibles. (I am here relying upon Elaine Pagels' book The Origin of Satan.

To borrow Tolkien's metaphor from "On Fairy Stories", there is much simmering in the great Cauldron of Story.