Debris

From Wildermyth Wiki

Debris looks like paper or cracked texture upon a floor title.

A tile with debris is flammable and can be lit up by a Torch, catch Fire from adjacent tiles, or ignited by a mystic. Fires on tiles with debris will not burn out.

Effects like Splinterblast produce debris in the target area.

Most, if not all, scenery will leave debris when destroyed. Using Salvage on scenery will also leave debris.