Pamela Isley (Earth-Prime)

"A poor man's version of Cluemaster, this questionable wordsmith turns green with envy when compared to me, the premier enigmatist. Is it: A, The Joker; B, Poison Ivy; or, C, The Riddler?"

- Cluemaster to Mary Hamilton, Ryan Wilder and Sophie Moore

Poison Ivy is a criminal and a former enemy of Batman.

Biography
At some point, Poison Ivy became an enemy of Batman.

She was later mentioned by the Cluemaster during a trivia game alongside The Joker and The Riddler.