March 19, 2015 6:18 AM EDT

Terry Pratchett didn’t fear Death. The British fantasy author, who died March 12 at age 66, wrote more than 70 books. And Death–the scythe-carrying, cloak-wearing, shepherd-of-souls kind of Death–was one of the most beloved characters in his wildly popular Discworld series. Pratchett’s Death loved cats, rode a horse named Binky and cared about the creatures who walked his fictional pancake of a planet. Pratchett’s books sold more than 85 million copies worldwide, and he was one of Britain’s best-selling authors of the 1990s. It’s easy to understand why: few fantasy authors have come close to creating a universe as vivid and expansive as Discworld.

But Pratchett was fearless in other ways. After being diagnosed with a rare form of early-onset Alzheimer’s disease in 2007, he became an advocate for medically assisted suicide and Alzheimer’s research. He continued to work, completing the 41st Discworld book last summer. “If I knew that I could die at any time I wanted, then suddenly every day would be as precious as a million pounds,” he said in 2010 of what he preferred to call “assisted death.”

“If I knew that I could die, I would live.”

–NOLAN FEENEY

This appears in the March 30, 2015 issue of TIME.

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Write to Nolan Feeney at nolan.feeney@time.com.

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