The possession ability is the poster boy for people's fear of psions. This ability allows a psion to gain full control over a person's mind and sense. The ability is performed like a mental attack and the target makes a mental save against the Excess of the psions skill check. If they fail, the psion gains control of the person as if it was their own body. This ability lasts until it is ended by the psion or if either the psion or the target takes at least a Serious Injury. If the subject dies during control, the psion must immediately make a save against 9 and suffer the mental scarring of experiencing death first hand.
Due to how the power works, any skill checks performed uses the psions skill values, but the physical values of the target. The psion is not able to access the conscious mind or memories of the target, as they are "mentally displacing" the target's mind, rather than diving into it. In addition, the person is not aware of the control taking place, as it feels as if they are asleep and dreaming. They are there and can perceive what happens, but it seems unreal.
Because of the immense focus and power required to fully supplant someone else's consciousness and also control their body, the psion can no longer control their own body or even use their own sense while in control of another. The psion will appear to be in a coma. All higher brain functions are focused on the target's mind and only the instinctual, life-sustaining functions remain to keep the body alive.