Thessaly was indeed a
witch in
The Sandman graphic novels by
Neil Gaiman. Despite her youthful appearance, she was quite
old, having made shadowy bargains to extend her lifetime by several thousand years. In her appearances in the series, she performed several interesting
rituals, usually involving
blood, if not actual
sacrifice. She was
pragmatic, self-protective, and quite humourless.
However, she played several key roles in the story arc of The Sandman, first as Morpheus' lover, in a disastrous affair that was probably a bad dating choice for both of them; and later she was pivotal in his ultimate fate.
She claimed she didn't love him, but she was crying as she said it.