After the Seraphim Castiel hesitated to follow her orders to kill the angel Samandriel, the angel Naomi brought him back to Heaven for further reconditioning. As part of this, Naomi created hundreds of clones of hunter Dean Winchester to have Castiel kill. Naomi's goal was to get Castiel to the point where he could ruthlessly and brutally murder his best friend so that she would know he was completely loyal to her.
After killing hundreds of these clones, Castiel came up against one that was making his way through the warehouse where all of the clones had been killed. Castiel knocked the clone to the ground, brutally broke his arm and then stabbed the clone to death with his angel blade. Entering the room, Naomi was pleased with the fact that Castiel killed the clone with no hesitation, making it quick and brutal. Naomi felt that Castiel was finally ready at this point.
When confronted with the real Dean Winchester in a similar scenario to the last clone, Castiel broke his arm in the same manner, but hesitated due to Dean's words before the angel tablet broke Naomi's hold over Castiel completely.
When Naomi was revealed to be alive years later, Castiel's experiences with the clones is one of the things he angrily confronted Naomi over. She simply called it and everything else he blamed her for "simpler times."
- The dead clones were seen lying in various positions throughout the warehouse in pools of blood.
- The last clone was armed with a replicated version of the real Dean's gun.