Scorpion venom
From Tardis Wiki, the free Doctor Who reference
Scorpion venom was a poisonous substance produced by scorpions. The Tong of the Black Scorpion extracted the venom for capsules. Members were required to ingest the capsule, should their circumstances dictate it so.
A Chinese man ingested a capsule given to him by Li H'sen Chang, after he was incarcerated by police. Later, Magnus Greel forced a capsule of the venom upon Lee after he failed to retrieve the trionic lattice. (TV: The Talons of Weng-Chiang)
