All hell breaks loose when an impertinent alchemist's experiment accidentally opens the gates to hell, and she stands face-to-face with Satan.

"When an impertinent alchemist enters hell in search of an elixir of life, can she find her way back out before Satan discovers her there?"

How about this?

It's interesting that you asked whether the motivation could be to save someone - in fact, in earlier versions of this logline that was explicitly stated as the character's motivation.

I will try a rewrite that more closely matches Richiev's suggested format.

Good re write by Richiev.

This is a simple concept with clear stakes and good characters the only suggestion I can make is to make it personal.

Could it be that the alchemist's motivation was to save her dying father, mother, sister, brother or lover?

Now to do so she must do soothing specific to defeat Satan in order to save the stakes character and the world?

After she accidentally releases Satan from hell, an impertinent alchemist must banish him once more in order to release her parents from demonic enslavement and save the world.

Hope this helps.