Steal Summoning

Warlock Invocation
Level: Dark, 6th
Components: V, S
Casting Time: 1 standard action
Range: Close (25 ft. + 5 ft./2 levels)
Target: One summoned creature
Duration: Concentration (up to 1 round/level) + 1 round
Saving Throw: None
Spell Resistance: No

With an act of will and the utterance of arcane syllables, you steal the nascent connection being formed between summoner and minion.
You steal control of a creature as it is being summoned.
If you succeed on a caster level check (DC 11 + the caster level of the summoned), you gain control over the target creature as if you had summoned it.
You must cast this spell immediately after the spell or spell-like ability that summoned the target resolves, before the creature takes even a single action.
If this spell's duration expires before the spell that summoned the creature ends, the target returns to its original master's control at that time.
If the original master is no longer available to control it, it becomes free-willed until its original master returns.

(Complete Mage, Page 124)