Joe

Joe is a drunken fighter who, during the time of Ultima IV, lives in Britain and can be found drinking in the Jolly Spirits with his friend Joe.

Upon providing Joe with some rum, he informs the Stranger that his friend Joe can help with the stones, and upon further inquiry will tell the Stranger that the yellow stone resides in Despise.

Trivia
There is a bug in the Apple II and C64 versions of Ultima IV (and probably the other 6502 ports as well), which makes the conversation with Joe unavailable.