Fungi, also known as mushrooms, are a type of fiend in Final Fantasy X and Final Fantasy X-2. Most members of the fungi family are vulnerable to fire, and in Final Fantasy X, they sometimes counter physical attacks with Pollen, which induces Sleep for three turns--and since they always attack with magic, this can prove to be very dangerous for your party.
Strategy
Final Fantasy X
Early in the game, it would be best to have Lulu use Fire or Fira on them--the latter should guarantee a one-hit Overkill depending on her Magic stat. Having Yuna Summon Valefor is also a plausible strategy, since Aeons are immune to sleep.
Final Fantasy X-2
This time around, they don't counter with sleep-inducing Pollen. However, they can inflict confusion, which is arguably worse. Early in the game, the simplest strategies are: use a Black Mage to cast Fire-elemental spells, have a Warrior use Flametongue to take advantage of the elemental weakness. Later, Yuna's Trainer dressphere can also exploit this. However, since most players won't need these strategies by the time they get to Chapter 3-4, at that point it might be best to simply attack with a Warrior, Samurai, or Dark Knight.
Fiends
Sphere Break
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