Psionic Conventionalist [Multiclass Encounter]

Heroic Tier
Prerequisite: 4th level, any class-specific multiclass feat for a class that doesn’t have the Psionic Augmentation class feature, Psionic Augmentation class feature
Benefit: You can swap one of your augmentable at-will attack powers for an encounter attack power of the same level or lower from the class you multiclassed into. You lose a number of power points based on the level of the at-will attack power: level 1–10, 2 power points; level 11–20, 4 power points; and level 21–30, 6 power points.

Published in Player's Handbook 3, page(s) 194.