Castle of the Winds

Castle of the Winds (COTW) is an old tile-based Roguelike Role-playing game (RPG) running under Windows 3.x, written by SaadaSoft and published by Epic MegaGames. The graphics are sixteen-colour icons and there are 34 spells (30 that can be learned without hex editing), 90 types of monsters, 3 towns, 40 dungeon levels (randomly generated), and many items.

It has a plot loosely based on Norse, but it's basically just about killing monsters (and buying/selling stuff to kill them with, or keep from getting killed.)

In 1998, the author Rick Saada decided to make it public domain and released the registered version for free (although this doesn't mean that the source code was released).