A thief teaches thief skills at the Black Dagger Guild in Old Fornost.

A thief is waiting here to teach his art.
>examine thief
He is a thief who has specialized in killing others as effectively as possible,
using all sorts of weapons.  His superior knowledge of how and where to use
them combined with his extraordinary stealth makes him a deadly opponent.

Skill list

Skill	Sessions	Difficulty
attack	11	Normal
dodge	5	Hard
hide	11	Normal
missile weapons	11	Normal
pick	1	Normal
piercing weapons	12	Normal
search	16	Normal
steal	3	Normal