Deadly Hazard (Levels 1–4)
When a rockslide occurs, every creature in its path makes a DC 15 Dexterity saving throw. On a failed save, a creature takes 11 (2d10) Bludgeoning damage, has the Prone condition, and moves with the rockslide. On a successful save, a creature takes half as much damage only.
When the rockslide stops, its space becomes Difficult Terrain, and all Prone creatures in its space are buried under rocks and debris. A creature buried in this way has the Restrained condition and has Total Cover. As an action, a creature can try to crawl out from under the rock pile. If the creature succeeds on a DC 15 Strength (Athletics) check, it is no longer Restrained; instead, it has the Prone condition and is atop the rock pile. If the check fails, the creature remains buried and gains 1 Exhaustion level.
A creature that has neither the Incapacitated nor the Restrained condition can spend 1 minute freeing another creature buried by the rockslide.
At Higher Levels. You can scale this hazard for higher levels by increasing the Bludgeoning damage as follows: 22 (4d10) at levels 5–10, 55 (10d10) at levels 11–16, and 99 (18d10) at levels 17–20.