Tyrion's mushrooms are a poisonous variety of mushroom found in a garden by Tyrion Lannister while he stays at Illyrio's manse in Pentos. The mushrooms grow from a cracked paving tile. They are pale white, with speckles and red-ribbed undersides dark as blood..
A Dance With Dragons
Tyrion discovers poisonous mushrooms growing in Magister Illyrio Mopatis's garden. He picks seven with a glove and stores them in his boot. Tyrion is skeptical when mushrooms are prepared by Illyrio's cook, but the magister assures them the food is not poisonous.
While heading down the Rhoyne on the Shy Maid, the angry Tyrion is tempted to put the slip the mushrooms into Griff's supper. After being kidnapped by Ser Jorah Mormont, Tyrion thinks he could eat the mushrooms and thereby avoid being taken alive to his sister, Queen Cersei Lannister. Tyrion is later sold on the auction block outside Meereen. Having no faith that Daenerys Targaryen could rescue him, he considers using the mushrooms on Penny and himself.
Tyrion attends Yezzan zo Qaggaz's hated overseer, Nurse, when he contracts the bloody flux. Nurse succumbs to the disease, but Tyrion is implied to have hastened his end by poisoning him. When Nurse falls ill Tyrion serves him soup "with slivers of mushroom in the broth." The last word spoken by Nurse is "No," to which Tyrion replies, "A Lannister always pays his debts.". It is unknown whether Tyrion still has mushrooms left.
Delicious, he thought, and deadly.—thoughts of Tyrion Lannister