Ankylosaurus

A living fortress of fused armor plates, low and broad, that simply weathers a predator's worst and answers with a tail-club heavy enough to shatter bone. Almost nothing can flip it, and almost nothing can crack it. It plods the fern prairies alone, head low, indifferent to the hunters that pace it because so few can do anything about it; pressed at last, it plants itself, tucks its soft belly to the ground, and waits with a boulder's patience for an opening.

Tail Club: bludgeoning, melee 10 ft, +1 to hit, 3d8+4 bludgeoning; the target is knocked prone and back 10 ft on a failed Dex Quick save, cooldown 1 round.

Armored Shell: encased in fused bone plate, resisting nonmagical damage; only its underside is vulnerable. Immovable: cannot be flipped, held, or knocked prone. Senses: Vibration Sense (feels movement, 30 ft), Dark Sense (30 ft).