You can regain power when you kill a creature.
Benefit: Once per day, as an immediate action upon reducing a creature to 0 or fewer hit points with one of your sorcerer spells, you can regain one usage of a sorcerer bloodline power that has a limited number of uses per day. The slain creature must have at least half as many Hit Dice as your sorcerer level. You cannot use this feat to gain another usage of a bloodline power that you have not yet used today.
Pathfinder Roleplaying Game: Ultimate Magic. © 2011, Paizo Publishing, LLC; Authors: Jason Bulmahn, Tim Hitchcock, Colin McComb, Rob McCreary, Jason Nelson, Stephen Radney-MacFarland, Sean K Reynolds, Owen K.C. Stephens, and Russ Taylor.