Talk:Red Solution/@comment-24057819-20150405064013/@comment-24821572-20150405071939

"It can be purchased from the Steampunker for during a Blood Moon or Solar Eclipse on a world that has The Crimson."

That means the worlds that start with crimson upon generation, not one brought into a corruption one. And nowhere in that article does it say you have to bring the NPC to the biome.