Choose up to six creatures within 30 feet that you can see to make a Wisdom saving throw against your spellcasting saving throw DC. On a failedIf they fail the save, a target takes 2d12 psychic damage, and, for the next minute, their speed is reduced to 0, they cannot benefit from any bonuses to their speed, and they are frightened of you. A target repeats the saving throw each time they take damage and at the end of each of their turns. These repeated saving throws do not cause an additional 2d12 damage and all the effects of this feature end upon a successful save. You may use this feature once per long rest.
In particular, some things I am thinking about are as follows:
Roundel of Inspiration is strong, granted it does require an action instead of a bonus action but that may not be enough. I could easily make it require more Bardic Inspiration Dice if that's a meaningful fix.
I'm honestly not too worried about the second feature, it is once per long rest, those affected can make saves rather often, and it doesn't deal even as much damage as fireball.
Magnum Opus on the other hand is the worry bringing feature. It effectively shuts down a battle one way of the other. If somehow all your enemies are affected (no legendary resistance) and they can't damage you with their reactions, it's basically a once per day "Win This Combat" button. I'm not sure how often that could happen, especially given that it also affects your allies, but I wonder if that makes it just too far gone.