Conversation so far:
Does Legion have a secret identity?
CANNOTANSWER.
What superpowers does Legion have?
psionic power.
What kind of psionic powers?
Jack Wayne, a swaggering adventurer, who commands David's telekinetic power.
Why does Jack Wayne control his power?
The trauma caused David's personality to splinter, with each of the personalities controlling a different aspect of his psionic power.
What was the trauma that caused this?
David was among the victims of a terrorist attack, in which he was the only survivor.
Where did the attack happen?
CANNOTANSWER.
Who else controls his powers?
Karami, Wayne, and Cyndi.
Who is Karami?
the terrorist leader, Jemail Karami.

Question: Who is Cyndi?
Self-contained rewrite: Who is Cyndi who also controls Marvel character Legion's powers?