But he was not even halfway to Hagrid when he saw it happen: Hagrid vanished amongst the spiders, and with a great scurrying, a foul swarming movement, they retreated under the onslaught of spells, Hagrid buried in their midst.
There are no more uses of "onslaught" in the book.
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They withstood the onslaught and counterattacked.
Her campaign did not survive an onslaught of attack ads.