Gus is Will's foster grandfather and the one who taught him sorcery and economics. He's a spectral sorcerer with a notoriously grumpy disposition—the kind of guy who really bristled at the idea of being bound by vows. When he did make his commitments, he pledged himself to Whirl, the God of Wind, asking for the freedom to live life on his own terms and actually enjoy it. That pretty much sums up his whole philosophy.
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