Source: Dragon #313
The concussive power of your Harden Energy effects is so strong that it drives opponents back.
Prerequisite: Harden Energy.
Benefit: You may add telekinetic force to any spell or power already enhanced by the Harden Energy feat.
An effect enhanced by Bull Blast can perform a bull rush against any opponent in its area. The spell's area or effect determines the direction of the bull rush: A line or cone pushes targets back along its length, but a spread or burst pushes them out to the edge of its radius. The enhanced spell or power has an effective Strength equal to its save DC + 1 per die of force damage it deals. Even a target that makes the appropriate saving throw to avoid some or all of the spell's damage is still subject to the bull rush.
To apply Bull Blast to a spell, the caster must expend 3 power points per spell level. To apply it to a psionic power, the manifester must spend 1 spell level per power level. Both of these costs are in addition to the cost of the Harden Energy feat. This feat may also be used in conjunction with Concussive Blast.