Very well-written. For the most part, this was biblically accurate, although of course there were discrepancies. I assume that you wanted that, but I will list them out regardless just in case.

1. God would have no reason to "fear" Nephilim, since he is all-powerful. If anything, He would wish to destroy them because they were born of demons and out of wedlock, and their sin would harm other people. God never kills needlessly.

2. Abdiel would never have been allowed to continue to guard the Tree after conceiving a child. Having chosen to disobey God, he would have become a fallen angel--a demon. You also mention that Abdiel does not have a choice in certain matters, but he clearly does. Otherwise, Abija would have never been born. For an angel, one sin is enough to condemn them. They have been in God's pure and untainted presence all their lives, and therefore have little excuse to do evil.

3. The Tree which God hid was to protect others from its sin. That being said, He has hidden it where absolutely no one would ever find it. It is guarded and some people even believe it to be underground.

4. The Nephilim, as far as I know, were not the only ones limited to one hundred twenty years. After the Flood, God limits people to these years as well, though it happens gradually. This doesn't necessarily mean that on the 120th birthday, you just die. It meant that you would grow old by them, when normally one didn't die of age until 900.

I do like your spin on the story, though. The way you wrote made it really sound like a biblical story. My four points above point out places where it doesn't match up--but then there wouldn't be much of a story, would there?

In any case, your writing was great, your spelling and grammar perfect. I think there was one place where you missed a question mark, but that's just a typo and an easy fix.

Obviously, you are a talented writer. And, you are very well-educated in the Bible. As a Christian, I normally find angel/demon fiction very silly, but this was very well-written, and more accurate than 99% of spiritual fiction that I read.