During the crucifixion, Jesus descends into Hell and must confront Satan to reclaim the keys to the kingdom.

I'm assuming that this is Biblically based, so you would want to correct that with "After being buried" as opposed to "During the Crucifixion".
Beyond that tighten it just a bit:
Prior to His resurrection, Jesus battles Satan for the keys to Death and Hell.

It might be a hard sell the way it's currently worded. Your potential buyers aren't going to expect symbolism to be there unless you tell them, and if you have to do that, your logline is going to be way too lengthy. You've chosen a very tough section of Scripture to work with; most Christians (I assume they're your target audience) will be very familiar with it, so you're going to have to be quite accurate in the retelling.
You might want to look at something that's tangentially related to the Bible, but not directly out of it. For example, about 15 years ago, there was a movie called "What Dreams May Come." It was very "new Age-y," yet it didn't get a lot of heat from the Christian community because it was religious without claiming to be Biblical. (Then again, it was a box office flop.)
If you're going to do something that's about a direct Bible story, you might want to see what DOES work. Recently, "Noah" was reasonably close to the Biblical account (although the "rock angels" were rather weird), and it posted a profit -- $356 million box vs. $125 million production budget. Even more so, "The Passion of the Christ" was very close to the Biblical account, and posted over $600 million worldwide against a $30 million budget.

Here's the interesting part, I said during because the crucification is part symbolism. Meaning defeating Satan was much more than what we see on the cross. I'm writing the story, showing him spiritually going to Hell and taking back the world, literally. I hope that made sense.