What Is This Potion?

It looks like someone drank it. Mattied, you want to take a go? I will take my best shot. It tastes like if you have taken a bar rag at the end of a shift and run get out into a bucket that had been used on the floor. What did it taste like? Oh, you don't know, Chris. Don't answer. If you want to make something up, I'll tell you if it's all right. Drink it. All right. Take a drink of soda pop. Roll me a constitution saving throw. Uh oh. He's gonna turn into an alien. 18. The only thing available here at the Flying Saucer Pub is soda pop