Warrick is the master of the Thieves' Guild in Ultima IX.
The Avatar found him on Buccaneer's Den in the guild house after Raven had applied a branding that initiated the Avatar into the ranks of the guild. Warrick offered the Avatar numerous scarce items of great worth for sale, and also was the best supplier of mandrake root.
However, after the Avatar freed the silver serpent, Warrick angrily denied the hero any more service, as the guild had been exposed following this act, and their business had taken great damage.