Indoors are usually more time consuming to sketch than the outdoors, so I quickly modeled the scene in Maya first and I kept it as a reference for the thumbnails.

For this concept I avoided the haunted, abandoned wights-infested type of crypt and I chose something more solemn instead, maybe a place where kings (and their treasures) were buried.
For these reasons I kept the ceiling a bit higher than normally seen in crypts, then I added details to indicate pride and power (i.e. the lion heads on the archways and the warriors sculpted in the columns) rather than religious icons like angels and such.

Since I didn’t have a briefing I decided to have fun and “tell a story” with the coloured sketch.
The scene is lit, so the place is obviously tended to, and the warm light on the left hand side of the drawing recalls the solemn and tranquil nature of the place.
The cold light on the right is where the action comes from, the crypt has been broken into and the moonlight (it’s clearly night outside) enters from a huge hole in the ceiling.

The broken column leads the eye towards the well lit burial chamber, where a thief is cautiously inspecting the treasure laid before the king’s tomb.
He doesn’t notice the guard-statues waking up to defend the crypt, so the shot is taken before some fighting – or running – action takes place.