Ultima III: Exodus
This guide is based on the PC version of Ultima III, though it is mostly applicable to all of the versions out there. While Ultima III not made in the same mold as its sequels, it is a solid RPG nonetheless. The interface and graphics are archaic, but for the first time in the series you're given a world to explore that doesn't seem like it is 90% extraneous. With interesting new party and combat systems, this is a PC RPG that's quite good for its time.
A step-by-step breakdown of your quest to learn about and destroy Exodus.