Credit to Decivre on the official forums. A sleight that allows asyncs to have some of the damage go to mental stress.
Psi Type: Passive
An async’s mind is heavily taxed when it produces active sleights, and the potential result is damage to the body. With this sleight, asyncs are capable of dedicating more mental resources to the task, which reduces the risk of bodily damage at the potential risk of the mind itself. Anytime strain is taken, the async may choose any amount of that strain to be received as mental stress rather than durability damage. Durability and stress damage caused by this is handled separately when determining wounds or derangements.