Defensive Shell( Complete Psionic, p. 60)
The psionic entity living in your mind enables you to better resist attacks.
A psionic entity takes up residence within your flesh. The entity grants you the following psi-like ability: Psi-Like Ability: 1/day--force screen or empty mind. Manifester level 1/2 your HD; save DC 11 + your Cha, Int, or Wis modifier.
You can use one or the other of your entitygranted psi-like abilities once per day--you can't use both. Once you use one, you can't use the other for the rest of the day.