Rotten fungus is obtained during the fight with Croesus. Its primary purpose is to use ten of them to poison one of the monster carcasses that Croesus is feeding off of, once they have been depleted of fungus. This will reduce the amount of regrowth to the carcass, as well as slow how quickly regrowing takes. It can be made by rotting the fungal building materials, timber, calcified, algae, or spores, as well as replacing the above if the player is damaged by the slime mould or the mushrooms that separate the corners of the arena.
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