NodeCraft
Max Mushrooms
From Pixelmon Wiki
Max Mushrooms are an item used to craft Max Soup, which, when given to a compatible Pokémon, allows it to gain a Gigantamax Factor.
When used in battle, it raises the Attack, Defense, Special Attack, Special Defense, and Speed of a Pokémon currently in battle by one stage each.
Max Mushrooms can only be found on mycelium in Mushroom Islands.
Usage
