Without alerting the other Masters of the Mystic Arts, Kaecilius and the Zealots moved through the library with the intent of stealing a spell to bring Dormammu to Earth. One night, Kaecilius and the Zealots went to the Kamar-Taj where they strung up the librarian and Kaecilius used his Scythe Daggers to behead him, dropping the librarian's severed head into a bucket underneath him.

He knew that the Ancient One herself drew power from the Dimension and believed her to be a hypocrite as she forbade others from doing the same. Kaecilius had heard of the Dark Dimension as a place without time where he and the Zealots would be immortal.

Kaecilius prepares to behead the librarian 'Master Kaecilius, that ritual will bring you only sorrow.' ― Ancient One to Kaecilius Soon enough, Kaecilius and his allies were able to defeat her and retook the Scepter from the thief before returning to Kamar-Taj to continue their training. Realizing he could not best her alone, Kaecilius joined Wong, Daniel Drumm and Tina Minoru to defeat the witch.

When the Dark Scepter was stolen by a Witch in London, Kaecilius at first tried to fight the witch herself but was easily defeated. Through twenty years of training with the Ancient One, Kaecilius became a trusted member of the Masters and with his skill, would also be trusted to train other students, though he was known for being particularly harsh and strict: At one point, he easily defeated and beat 6 apprentices and dismissed Mordo's disapproval of his harsh training, saying that they project their advances too predictably and needed a lot more training. 'That relic you hold has far too much power to be contained by someone who doesn't fully comprehend the mystic arts.' ―Kaecilius to Witch

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