Janis thorn

Janis thorns were small, poisonous thorns used by the Sevateem as weaponry. Their poison caused first paralysis and then death in humans. Though there was no naturally occurring cure, an anti-toxin was created by the Fourth Doctor using a bioanalyser. (DW: The Face of Evil)

Leela frequently used janis thorns, which she fired through a blowpipe. In Victorian London, she used one to kill a Chinese assassin threatening the Doctor. (DW: The Talons of Weng-Chiang)

Leela threatened a death-dealer named Jason with a janis thorn. (ST: Death-Dealer)

Leela still kept her janis thorns when she was living on Gallifrey. (NA: Lungbarrow)

When knocked unconscious, the Fourth Doctor mumbled, "No more janis thorns", even though she had long since left him. (DW: The Pirate Planet)