Thunder-Lizard Colossus

A sauropod grown to mythic, mountain-shouldering size, so vast that storms wreath its back and its tread sets off rockslides on distant slopes. The old songs say one walking is mistaken for the land itself moving. It follows ancient migration roads worn into bedrock by ten thousand years of its kind, and villages in its path are simply abandoned for a season - it means no harm and notices no one, which is precisely the danger.

Colossal Stomp: bludgeoning, melee 10 ft, +3 to hit, 4d10+8 bludgeoning (save Dex Quick for half). Thunderclap Tail: thunder, melee 30 ft, it cracks its tail like a whip, dealing 4d8+8 and deafening and knocking prone all in a line on a failed Dex Quick save, cooldown 3 rounds.

Earthshaker: every step quakes the ground within 60 ft (creatures save Dex Quick or fall prone). Mythic Bulk: immune to being held, moved, or knocked prone; resists nonmagical damage and shrugs off the first spell to strike it each round. Senses: Night Vision (60 ft).