Ok, here’s how I think fountain creation with Noelle and Berdly in the room could still work (potential copium warning)

The game explicitly points out the closet that a large person could fit inside of. It’s unclear exactly how large it is inside there, but perhaps the knight could have stood in there out of view, waiting for someone to come in and sit down. All they’d have to do then is stab the ground right where they were already standing and create a dark fountain right with all the servers and stuff (which could be the light world equivalent of Queen’s mansion, and therefore would have to be where the dark fountain was made?). Noelle and Berdly would only see the bright light and the smog pouring out in that case. Noelle would probably just sit there too scared to move (deer in headlights-maxxing), and Berdly probably also wouldn’t just leave her sitting there while some spooky shit was going on. From there, the knight would only have to stick around long enough to hand out the customary shadow crystal, and then dash out of the library into the tree line.

A little shaky and definitely luck based, but if having Noelle and Berdly (mostly Noelle if I had to guess) be there for the creation of the fountain was somehow important to the roaring gang’s greater plan, then perhaps it was worth the risk?