Deep Dungeon: Madou Senki/Floor 3

Key Points

 * 1) At (0, 15), you will find a merchant who will sell you a compass.
 * 2) You will find the key that opens the locked door on Floor 1 at (27, 4).
 * 3) All around this point is the underground market.  If you possess the Mark Ring, you can advance to Floor 8 by proceeding to (6, 22).