Acid Dye

A dark green ripple washes outward across whatever you put it on, which reads far better on a large flat sprite like wings or a cape than on a small weapon. Anything wearing it stays visible in unlit rooms without actually giving off light, so it will not help you see where you are going, but your character will not disappear into the dark either.

Put any of the three acid dyes on a Shadow Orb and parts of the sprite stop drawing, sometimes the whole thing. Bug or not, it is the usual way to keep a light pet following you without the glowing ball bobbing in front of your character while you aim.

It comes out of the Dye Trader in exchange for a Strange Plant, and which dye he hands back is random. There is no way to aim for this one, so expect a pile of duplicates before it turns up.