Quy'Tek

The Quy'Tek mediations is a dark side technique used to shield one's presense in the Force. When properly applied and maintianed, a Sith Lord or Dark Jedi can mask their own dark signatures appearing completely benevolent to even the most powerful and alert Jedi.

Darth Sidious is the most notorious user of this power, having hid his dark nature for decades from even the Jedi Council. Other known users include Darth Tyranus and Asajj Ventress.