Fogbound Dye

He only carries this while he is standing in a Graveyard, which means you have to build him one. Clustering enough Tombstones near his house flips the area over, and the biome brings its own gloomy screen filter with it. Set the graveyard up once, buy as much as you think you will ever want, then break the stones so your town goes back to normal.

It drains the color out of whatever it is applied to and lays a drifting haze over the sprite. On bright armor it reads as faded rather than gray, which is the effect most people are after. On something already dark it flattens the detail into a single smudge, so it is worth testing on the piece before you commit a stack.