Once your character is adequately supplied with food, light, armor, and weapons, they are ready to enter the dungeon. Move on top of the > symbol and use the “Down” command (>).
Your character will enter a maze of interconnecting staircases and finally arrive somewhere on the first level of the dungeon. Each level of the dungeon is fifty feet high (thus dungeon level “Lev 1” is often called “50 ft”), and is divided into (large) rectangular regions (several times larger than the screen) by permanent rock. Once you leave a level by a staircase, you will never again find your way back to that region of that level, but there are an infinite number of other regions at that same “depth” that you can explore later. Monsters, of course, can use the stairs, and you may eventually encounter them again, but they will not chase you up or down stairs.
In the dungeon, there are many things to find, but your character must survive many horrible and challenging encounters to find the treasure lying about.
There are two sources for light once inside the dungeon. Permanent light which has been magically placed within rooms, and a light source carried by the player. If neither is present, the character will be unable to see. This will affect searching, picking locks, disarming traps, reading scrolls, casting spells, browsing books, etc. So be very careful not to run out of light!
A character must wield a torch or lamp in order to supply his own light. A torch or lamp burns fuel as it is used, and once it is out of fuel, it stops supplying light. You will be warned as the light approaches this point. You may use the “Fuel” command (F) to refuel your lantern (with flasks of oil), and it is a good idea to carry extra torches or flasks of oil, as appropriate. There are rumours of objects of exceptional power which glow with their own never-ending light.
These last two paragraphs apply to most classes, but not to necromancers. Necromancers dislike light, and shroud themselves in darkness. They are usually better off not carrying a light, but also do not gain any of the bonuses that may come from magical light sources.