Trial Stew is an item in Paper Mario: The Thousand-Year Door and Super Paper Mario.
Appearances
Paper Mario: The Thousand-Year Door
One may think that this item is completely useless, seeing as it lowers the player's hit points and flower points to basically nothing, but that isn't the entire case. This is the only item in the game that fills up your Star Power, so it's not entirely bad. This item is only created by mixing both the Couple's Cake with a Poison Shroom.
Super Paper Mario
This item reappears in Super Paper Mario. Since there aren't points for flower power and star power, its effect is a little bit different. Instead, this item uses a unique power to automatically poison Mario. Upon doing so, however, Mario gets 100 Points every time he takes damage from this special poison. The poisonous powers can still end up killing Mario if not treated soon enough.