Purification Powder

The three thrown powders convert blocks and walls in a small cloud where you aim. The reach is about the length of a broadsword swing, so this is close work. You are standing next to whatever you are converting, and the cloud lights the area while it hangs there.

Purification Powder undoes conversion in every direction: corrupt, crimson and hallowed tiles all revert to their plain forms, so ebonstone becomes stone, crimsand becomes sand, pink ice becomes ice. The Dryad sells it, though not while a Blood Moon is running.

The most useful thing purification powder does has nothing to do with cleaning up your world. Ebonstone and Crimstone resist a starter pickaxe, and the usual answer is to beat the world evil boss first so you can build a better one. Powder sidesteps that entirely: convert the stone to something ordinary and tunnel straight down to the Shadow Orbs or Crimson Hearts. Explosives are the only other way through that early.

It also has two conversions that have nothing to do with terrain. Throw it at a Tortured Soul in the Underworld and he becomes the Tax Collector. Throw it at a Mystic Frog and you get the Mystic Slime town pet. Both are one way trips, and both are the only route to that NPC.

Vile and Vicious Powder do the reverse job for their own world evil, pulling pure and hallowed tiles across to their side. Each is crafted from its matching mushroom or bought from the Dryad during a Blood Moon in a world of that type. Thrown at a Bunny, Penguin or Goldfish they produce the corrupt or vicious version of that critter, which is by far the easiest way to get those for banners or for a jar on a shelf.

• Purification will not clear corrupt or crimson thorn bushes. Those still have to be cut by hand, and they are what spreads while you are busy elsewhere.
• Powder applied to Vile Mushrooms growing on corrupt jungle grass gives back Jungle Spores.
• The Dryad stocks none of the three in a Remix world, so plan around crafting there.