Pretty decent and simple spell. It's well coded.
The only thing I have to say is that in HC Counter you're setting variables
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Set Variable Set HC_Unit = DamageEventTarget
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Set Variable Set HC_TempData = (Custom value of HC_Unit)
when they're not necessary at all here. You're only using custom value of unit once. As for the other variable, DamageEventTarget already does the job, while at same time you're using it when causing damage.