"APPLY POISON" CLEAN

Usage:         apply <poison> <weapon>
Cost:          poison vial
Duration:      4 minutes
Level:         Thief 31
Manual:        alchemist's handbook
See Also:      SLEIGHT OF HAND POISON TYPES 

Thieves may apply poisons to their weapons, making a deadly combination.
The poison only takes affect when the thief backstabs the target, as
only backstabs can deliver the poison deep enough into the target's
system.  When applying the poison, you must have the poison vial in your
inventory.  A thief, however skilled, may apply two doses of poison at
a time.  Keep in mind, if not used, the poison will evaporate and disappear
in time.

In the course of his training in brewing and application of poisons, a
thief will learn to recognize the type and freshness of poison on a
blade (just type 'examine <item>'), and also the proper safety procedures
for cleaning off poison.  To clean poison off of a weapon, just type
'clean weapon'.