Unless I'm misunderstanding how the feat works, Psionic Mania should make the next PSI attack crit (assuming it is a PSI attack that can crit).
However, Plasma Beam does not always crit after using Psionic Mania, even though it can crit. I'm currently testing it against Naga Protectors, who can be critically hit with other Metathermic PSI attacks.
Is this a bug or intentional?
