Spoilers ahead.
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There was William Miller, monk and healer.
He got the nickname Nicodemus the Gnostic for how much he smoked and his constant questioning. (This is blatantly inspired by my own dad, William Nock, who got his 'nick'name in the Air Force because he picked up a nicotine habit in order to take advantage of more frequent breaks. They called him Nicotine Nock. When I was growing up, friends just called him Nick.)
He was not famous, though.
During the war, still as Nicodemus, he was convinced he was right, and kept tending to wounded eladrin (and poisoning ones who weren't useful) until he persuaded Kasvarina to join him. That ended badly, with him dying, her daughter being killed as an avatar of Srasama, and Kasvarina herself seeing her people devastated.
Around 17 years later he was operating under the name William Miller again, having possessed some schmuck and taken his body. Then he got burned alive on his pyre. He abandoned the William Miller identity.
Back to being Nicodemus, he founded the Obscurati with Kasvarina and the first Jierre, both of whom knew who he was.
Since "William Miller" was the prominent historical figure, Nicodemus has never told anyone (at least, no one he let live) that he was Miller. But he goes by 'Nicodemus' and smokes Leaf of Nicodemus (which, to be clear, he didn't invent or anything). Since it's a conspiracy founded on secrets, everyone assumes it's a Nic-name.
Though really, only the ghost council and the heads of the cells even know he exists. He would tell them at least the basics of the story of why he and Kasvarina founded the Ob to topple the Clergy. So they'd know he went by Nicodemus the Gnostic for a while.
Now he's just Nicodemus, though maybe a cell leader in adventure 7 might call him "Nicodemus the Gnostic," and he could laugh at that old name being from his days as a monk.
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