The mask is in pieces - only that and a quickly-dissolving shadow remain to show that the Knight ever existed. That, and a changed world.

Hornet doesn't have to look outside to know that the Crossroads are dark and safe once more, haunted only by memory and the fallen husks of the bugs the Radiance had once controlled. Whatever Hallownest will become now, thriving world or mausoleum, it will at least no longer be an infected nightmare. And all it took was one last little sacrifice.

Hornet kneels, and reaches out to the broken halves of the Knight's mask. She does not weep.