It's just an overgrown mushroom, this thing is pretty sturdy—[A few light taps as if to prove his point and to be fair, it is a rather heavy mirror.]—and...I think it's distracted by its reflection, actually.

[Going to mentally take a "look" through the mirror and—no, that's a nearby window—okay there.]

And if it does try to escape, I can pop right through the mirror to grab it. Or distract it long enough for you to notice and come back, anyway.

[Not even going to pretend he's a pro mushroom wrestler, but he would do his best.]