Door

Doors separate rooms from each other (though they may simply be placed in the middle of a room as well), and are found in the Dungeon and some branches. They are set into walls, and are usually only 1x1 or 2x1 (though some vaults may contain far more massive doors). Walking into a door will open it, while pressing C when adjacent to one will close it. If you know that there are monsters behind a door, leaving it closed will keep them at bay unless they are aware of you and are intelligent enough to open the door, or they are capable of simply eating the door, in which case it will do you very little good. Some "doors" may also attempt to eat you, which is probably even worse.

The dungeon contains many hidden doors as well. These cannot be seen normally, but become visible if you spend enough turns near them. You automatically search as you move around the dungeon or rest in place. The . key lets you rest/search for a single turn, while the 5 key does so for up to 100 (spotting an enemy or finding a door or trap will interrupt this). The Traps & Doors skill makes search attempts more likely to succeed, assuming there is anything there in the first place.

Doors may occasionally creak when opened, alerting nearby monsters to your presence. This is less of an issue for heavily armoured bruisers than for stealthy sorts, as they tend to wake up everything no matter what. Fortunately, the chance of this happening is 1 in (Dexterity + (Stealth + Traps & Doors)/2), so stealthy characters are unlikely to cause it anyway.

Tips & Tricks

• Closing doors in front of monsters will delay them slightly even if they are able to open the door. If you are trying to buy time for one more MP or for a teleport to kick in, this can be a life saver.
• If you open a door and immediately see out-of-reach enemies capable of smiting you, tormenting you, blasting you with hellfire, or otherwise dealing heavy damage at range, don't retreat! Running gives them the opportunity to attack you as long as you're in their line of sight. If you close the door first, this forces them to come to you, robbing them of several turns they could otherwise spend blasting you, and guarantees that you'll get to act against them first. This is effective against early threats such as orc priests, as well as late-game fiends and liches.
• If you find yourself on a new floor and reach a dead end before coming across anything of interest, searching at the dead end will often reveal a hidden door.