If there was one thing that Corey was certain about as he fought Aethara, it was that he was going to use Aethara to create an abomination with his Nightmare Finger.
After Aethara's transformation to the Fallen Angel of Rot, Corey was surprised when he sensed that he could use Aethara's corpse to create an abomination with his Nightmare Finger.
However, when he thought about it, Aethara was no longer purely human, but a hybrid of a Tainted and an abomination.
Corey already had the corpses of the Capra King and the Temple Guardian in his Tri-Pupil Eyes, and he planned on using their corpses to create abominations that could grow alongside him.
He had never created an abomination before, and he was curious and intrigued by what would appear and happen when he created an abomination.