Water Walk. Terratrum can walk on water, as with the effect of the water walk spell.

Worm. Terratrum can move over difficult terrain without expending extra movement.

Elemental body. Terratrum can burrow through rock without leaving marks or tunnels in the stone.

Multi attack. Terratrum can make 4d4+3 attacks, 4d4 with it’s claws, 2 with its bite and one with its tail.

Claw. Melee weapon attack: +15 to hit, reach 5 ft., one target. Hit: 2d6+10 slashing damage.

Bite. Melee weapon attack: +15 to hit, reach 5 ft., one target. Hit: 5d6 piercing damage, target must succeed on a DC 25 strength saving throw or be grappled.

Tail.Melee weapon attack: +15 to hit, reach 5 ft., one target. Hit: 8d8 bludgeoning damage, target must succeed on a DC 25 strength saving throw or be forced back 10 ft and knocked prone.

Swallow. Terratrum attempts to swallow one creature it is grappling. It makes a Strength check contested by the targets dexterity check, the target makes the roll with disadvantage. A creature swallowed is blinded and restrained and has complete cover from outside effects, at the start of each of its turns a swallowed creature takes 28 (8d6) acid damage.   If Terratrum takes 60 damage in a turn from a creature inside it, it makes a DC 18 constitution or vomit out all creatures inside it. 

Shake earth.(Recharge 5-6) Terratrum burrows under the ground and the earth in a 30 ft diameter 10 ft high cylinder starts to shake. Any creature in the radius makes a DC 17 constitution saving throw. On a failed save, the creature takes 8d8 bludgeoning damage and is knocked prone, and takes half as much damage on a successful one. The area then becomes difficult terrain.

Dash. If a creature moves within 5 ft of the Terratrum, it can move up to thirty feet away or burrow underground, without provoking an opportunity attack.

Tail Lash. When the Terratrum is attacked, it can use it’s tail attack on one creature within 5 ft of it.

 Terratrum can take 5 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn. Terratrum regains spent legendary actions at the start of it’s turn.

Bite Attack. Terratrum makes a bite attack with advantage.

Claw Attack. Terratrum makes 3d4 claw attacks.

Earth Shake.(Costs 3 Actions)Terratrum uses it’s earth shake attack.

Spit Acid.(5 Actions) Terratrum spits acid at target within 15 ft of it. Target takes 12d8 acid damage and is paralysed until the end of it’s next turn