Hmm..but the Vong are technically outside the universe already. Everything in the universe exists as part of the "force." The Vong however are not part of the force.
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When the darkness comes, keep an eye on the light no matter how far away it seems.
At the point of DE, this is Palpatine in his younger body and able to move faster than the eye can perceive when he fights Luke...this isn't an easy victory for Shimrra if it is one at all
He was "outclassed" against Luke and only used the force storm as a last resort. What makes you think he is going to think a regular monster like Shimrra would pose a threat.
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When the darkness comes, keep an eye on the light no matter how far away it seems.