Although there are only a few possibilities, upon careful analysis, many can be largely ruled out.
For example, hysteria.
While it's possible for one person to experience hysteria, the likelihood of a group of people all experiencing it is quite small. Of course, collective hysteria can occur, but it requires external suggestion and influence as a prerequisite.
If such a "suggestion" truly exists, it indicates that there is certainly something fishy behind the event, warranting further investigation.
The possibility of a mirage is also very small. The prerequisite for a mirage is the existence of the "object" itself, to remotely create an illusion.
But does the Crystal Origin of Dreams really have "translucent undead"? At least, Angel hasn't discovered any yet.
Therefore, if you ask Angel, the greatest possibility still lies with the Fairyland Duplication.
"Why don't we take another look?" suggested the Rabbit Girl.
