The boys were all eaten up with envy—but those that suffered the bitterest pangs were those who perceived too late that they themselves had contributed to this hated splendor by trading tickets to Tom for the wealth he had amassed in selling whitewashing privileges.
There are no more uses of "amass" in the book.
Show samples from other sources
On one side of her, a torch-juggler has amassed a large crowd, and on the other, a Tribal Kehanni spins her tales, her voice rising and swooping like a bird in flight.
Sabaa Tahir -- An Ember in the Ashes
His bed wasn’t made, there were clothes amassed in a corner, and several dirty plates were piled on his side table.