This is a new brush entity that was added with the christmas update and is currently in cp_degrootkeep. If huntsman snipers go through it (or look at it?), their arrow becomes ignited However, using this entity in a custom map doesn't seem to work. I literally copy pasted the brush from degrootkeepr, and passing through doesn't do anything. Is anyone willing to figure out what's going on? I hope it's not hard-coded in the map or something.