Endless Rockslide

A perpetual cascade of stone and earth, from pebbles to boulders, begins near the peak of a mountain and tumbles down the slope before disappearing into a crevice. This Endless Rockslide originates from the Elemental Plane of Earth, emerging from a planar portal near the mountain peak and plunging through a second portal deep in the crevice, ending in a different area of the Plane of Earth.
Giants sought to harvest the rockslide’s magic and endless mineral resources. To aid their work, they carved walkways around the rockslide and built stone bridges spanning the fissure it pours into. The Giant runes these folk carved into the bridges glimmer with crystalline light as they harness elemental earth magic.

Description

The Endless Rockslide plunges down the mountainside with tremendous force and thunderous sound. Creatures within 100 feet of the earth slide make ability checks that require hearing with disadvantage. A creature that starts its turn in the rockslide must make a DC 20 Strength saving throw. On a failed save, the creature descends 200 feet and takes 33 (6d10) bludgeoning damage. On a successful save, it takes half as much damage and can grab a stable handhold within reach to avoid descending. After descending 1,000 feet from the rockslide’s origin, the creature passes through a permanent portal to the Plane of Earth. A creature with a burrow speed can use that speed to move in the slide, has advantage on the saving throw, and takes half damage on a failed save and no damage on a successful save. A creature with the Earth Glide trait automatically succeeds on the saving throw. The source of the slide is also a permanent portal to the Plane of Earth.
Bridges and Walkways. Bridges carved with Binding Runes (see below) span the chasm, and walkways allow access around the rockslide. A crane and winch with buckets and sieves, installed in recent times, allow workers to gather minerals from the slide.
Chambers. Giant-sized chambers are carved into the rock near the falls, including a workshop that holds tools for working metal, stone, and gems.

Features

The Endless Rockslide has the following properties:
Binding Runes. A creature touching one of the runes on the bridge can attempt to activate it with 1 minute of concentration and a DC 20 Intelligence (Arcana) check. On a failed check, the creature takes 22 (4d10) force damage, as the bound elemental power releases explosively. On a successful check, the rune conjures an earth elemental that remains for 1 hour and obeys the creature. Once a creature has used this property to cast the spell, that creature can’t use this property of any binding rune again until it finishes a long rest.
Endless Resources. The Endless Rockslide is an inexhaustible source of minerals. A creature who spends 8 hours using appropriate tools to gather materials from the slide acquires 2d6 × 50 gp worth of useful or valuable minerals.