Wish there was more info on what critter gets the most out of it. I used a stone on my Creepy Crate just because, and my health went up 5
I got a universal stone and thinking of doing it on someone I don't want to farm again (Baby Ape? Spawn of Onxyia?) Also wondering if a grey would get more out of it then a green or if it's a static upgrade. Trying to save my stones till i get more pets, maybe then it will be obvious or more info will be out there.