You imbue a weapon with the power to drive foes back. The first time each round the weapon strikes a creature, the weapon attempts a free bull rush combat maneuver check against that creature. This does not provoke attacks of opportunity. The combat maneuver for the bull rush is equal to 1d20 + your caster level. You do not have to move to push creatures more than 5 feet with this bull rush. If a creature you strike has spell resistance, you must attempt a caster level check to overcome its spell resistance the first time you strike it. If you fail, that creature is immune to the effects of this casting of _banishing blade_. The first time each extraplanar creature whose Hit Dice don’t exceed your caster level is driven back at least 10 feet by this spell, it must attempt a Will save. If it fails, it is sent back to its home plane. Whether it succeeds or fails, that creature is staggered for 1 round and _banishing blade’s_ duration ends.