You’ve traveled this way before but the street you thought was clear now ends in a 50 foot stone wall. Turning back the way you came you see a group of small rocklike men a hundred feet down the road. They reach their arms into the stones of the street as if it were liquid and grab hold of something. As they lift together a 5 foot section of wall rises as a single piece across the entire length of the street. They repeat this action and are soon lost behind 10 feet of wall. A quick glance from side to side reveals the nearby alleyways are already blocked off…
The party starts 120 feet from the wall which is already 10 feet tall, which is growing at a rate of 5 feet per round. The wall is magically smooth and shear and requires a DC 20 Athletics check to climb unassisted. A grappling hook can be thrown to the top or to an object on the other side with a DC 17 Strength/Dexterity thrown weapon check. Successfully attaching a grappling hook and rope decreases the climb check to DC10.
The wall stops growing at 50 feet. Characters must both safely climb up and down the other side, taking appropriate damage for failing the climb check and falling off.
If the characters cannot climb or want to seek another way around they can navigate the maze created by the wallers with 3 successful DC16 Intelligence checks. Each failure causes the party to spend an additional 2 hours of fruitless exploration and they gain 1 level of fatigue. (3 levels of fatigue = 1 level of exhaustion).