I’m not sure if this is a logline problem or a story problem, but you start with the threat (antagonist) being an ancient spell book, then you end with the threat (antagonist) being a voodoo witch doctor.

I would stick with one or the other.

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“When a witch doctor uses a family heirloom to steal souls, an occult librarian teams with an un-dead cop to steal back the relic and deactivate it forever.”
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Hope this helps, good luck with this!

I believe it’s better to start with the event which gets the story going, however your latest attempt was pretty good and definitively usable.

How about this, I shuffled what you wrote just a little bit:
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When her twin brother is kidnapped, a candle maker with developing magic powers must enter a dark realm of monsters before an evil sorcerer uses him to destroy their kingdom.?
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Hope that helped, good luck with this!