From A Wiki of Ice and Fire
Greycap is a poison made from a toadstool.
A Clash of Kings
Tyrion Lannister sees powdered greycap in Grand Maester Pycelle's collection of medicines and poisons.
A Storm of Swords
During Tyrion Lannister's trial for the death of King Joffrey I Baratheon, Pycelle claims that Tyrion stole a sample of greycap as well as other drugs from Pycelle's collection.
- ↑ 1.0 1.1 A Storm of Swords, Chapter 66, Tyrion IX.
- ↑ A Clash of Kings, Chapter 17, Tyrion IV.