Lucifer woke up from his slumber, possessing a new energy core in his heart. However he remained oblivious to what this core was truly capable of. Until now, he had been able to use all his cores freely, and even when he stole other people's cores, he was still able to grasp them.
With those abilities, he was able to learn how to use them as if they were a part of his body, but with this new ability, he found himself struggling. He couldn't understand this core. Instead of feeling like it was a part of his body, he felt that it was something external.
It was akin to a weapon that he could hold but not freely wield, as if the energy core had a mind of its own, resisting Lucifer's attempts to understand and harness its power.
He didn't know what it was or how he received it, but one thing was clear as day. This thing was special in its own way. While his other abilities could be restricted by anti-magic stone, this thing couldn't.