Brogue Wiki
The cold marble statue has weathered the years in grace.

Cracks begin snaking across the marble surface of the statue! The statue shatters!


@ pauses to admire the craftsmanship.

Marble statues are scattered throughout the dungeon, usually in a wall recess.

Most marble statues are in fact just statues, but some statues are more than they appear. These special statues have a trigger tile, and when that tile is stepped on cracks will begin to form on the surface of the statue. A few turns later it will burst to reveal whatever was contained within. These are either placed randomly or as a component of a key/door trap. 

Special statues start appearing as early as level 6. The statuary key/door puzzle won't appear until at least level 10. Worms in the walls and Sentinels won't show up until level 12 at the earliest.

Telepathy allows you to detect that there is a monster within a statue before the trap triggers, but not what type of monster it is. What a statue turns into, if it's not part of a worms in the walls contraption, depends on the dungeon level:

The monster in the statue may be out of depth. For example, a wraith may appear in a statue on level 7.