A trap that affects more than one place at a time, built by Justice Light beneath the castle.
Baroness Victory revealed that Justice Light had built a trans-dimensional trap right underneath the crawlers' castle, decorating it with regular traps so that Rosetta never noticed it among them.
Donut asked what a trans-dimensional trap even is. Carl explained: it's a trap that affects more than one place at a time, at least here in the dungeon. He added that while Justice Light was willing to use traps that way, something told him the man had something much bigger up his sleeve.
Justice Light's concealed multi-location trap, and the clue that he is planning something larger.