Bastila Shan, Fallen Jedi

Whenever Bastila Shan, Fallen Jedi or another
Sith enters the battlefield under your control, tap
up to one target creature. That creature doesn't
untap during its controller's untap step for as long
as you control Bastila Shan.
"The dark side calls to you, Bastila; you hunger
to taste it. Become my apprentice, and all its power
can be yours!" — Darth Malak