User blog:Sasha Dawg/Mod Idea: Potion Maker NPC

Wouldn't it be nice if you could get a potion seller in Terraria? And you have to get him in hard mode by finding him bound in the underground hallow somewhere? I think that would be nice. He sells you (at first) gravitation potions, healing potions, and regeneration potions. For every hard-mode boss you kill for the first time, he'll get two new potions to sell. I was thinking that there would be one potion that you can only get from him after killing ALL of the bosses, but I'll need suggestions for what it is. Comments?