X pauses fractionally, flicking a glance at Bruce that's just quick enough to meet his gaze and hold for a second. Then she speeds up her pace, slipping past the rest of the party in order to take point.

Bruce can take rear guard. Someone needs to watch their back.

And anything or anyone that is waiting down through that trap door --

X will smell (and hear) them coming.

Her primary goal, after all, is to keep Amy (and her friends) safe. Spell-breaking is for the professionals.