Hide

Trappers, lurker aboves, and various piercers can innately hide. All spiders except giant spiders and all snakes except water moccasins can hide under objects. Mimics can disguise as objects, which is related. All water creatures can hide in water.

If you are polyselfed into such a creature, you can use the #monster command to hide.

Searching or throwing objects is guaranteed to reveal their position. Searching causes them to stick to you if applicable. Gold is good to throw because it is abundant, does not risk breaking pacifist conduct, and gets you credit in stores.

Attempting to move onto a seemingly empty square with a hider on it causes you to waste a turn without attacking it. This also goes for movement with the m command (sometimes except if you are warned of the creature).