Triggered Event

There’s nothing quite as irritating for players as when they  burst in a door, ready to kick some Big Bad Evil Guy buttocks, and the DM launches into a short novella of description and monologue. Some description is nice, especially if it contains information the players will want to know before they charge farther in (the floor is hot lava, the demon is in an unbroken chalk circle) but too much information risks burying vital information beneath flowery descriptions of the odour of the room and sound of water dripping on mildew.