The spirit asleep in Mount Ghakis, walking: a heap of the mountain's own stone in the shape of an old man, three times a man's height, with a hole in his chest where something used to be. He isn't angry. He's looking for his heart.
Legendary Resistance (2/Day). When Grandfather Stone fails a saving throw, he can choose to succeed instead, twice a day.
Earth Glide. Grandfather Stone can burrow through nonmagical, unworked earth and stone without disturbing the material he moves through.
Looking for His Heart. The mountain folk say Grandfather sleeps in Ghakis and keeps the passes open. Since the count's quarry dug out his heart he walks, and he doesn't see what's in his way.
Actions
Multiattack. Grandfather Stone makes two Slam attacks.
The Ground Shrugs. Dexterity Saving Throw: DC 17, up to four creatures within 30 feet. Failure: 22 (4d10) Bludgeoning damage and the Prone condition. Success: Half damage only.
Lair actions
Rockfall. The quarry's cut faces give way over two creatures: each makes a DC 15 Dexterity saving throw, taking 11 (2d10) Bludgeoning damage and falling Prone on a failure, or half the damage only on a success.
The Floor Opens. The quarry floor opens round one creature's legs and closes again: it makes a DC 15 Strength saving throw or has the Restrained condition until the end of Grandfather Stone's next turn.