A thief teaches thief skills at the Thieves' Guild in Tharbad. The entrance is located behind a hidden brick opposite the weapon shop.

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	16	Normal
dodge	23	Hard
piercing weapons	12	Normal