How does one kill this thing? I have all 4 wands, but cannot figure out how to use them to whack him.

Are you referring to the construct in Chapter One that Eltoora has you fight? ( I don't have it installed on my laptop presently... it isn't supported, so I can't open the module and check for you).
If you are, then I really don't need to warn for spoilers, do I?
If you aren't, disregard this.
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Eltoora told you to collect the wands, and to mark well the order. Look over your journal, and you'll see that her exact words are written down. Think it over.
Mark well the order, and you do, so conveniently in your journal.
If you can't figure it out from THAT, then...
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Just use the wands in the order Eltoora said.