Colossal Mud Snail

Ceramic Shell: While inside the shell the Colossal Mud Snail has a +5 AC, resistance to fire, cold and ligthing damage and is speed is reduced to 0.

While inside its shell it cannot use any of its actions other than Stalk Slam.

Sticky Mud: The Colossal Mud Snail can walk on uneven surfaces without movement penalty and without having to roll for acrobatics.

Elemental Beast: The Colossal Mud Snail is considered a beast and an elemental for effects that require either creature type.

Trampling Beast: The Colossal Mud Snail can move throw the spaces ocupied by other creatures and objects smaller than it all creatures it moves throw must succeed in a DC 17 Dexteirty saving throw taking 4d10 bludgeoning damage on a failure.

A creature that fails this saving throw must succeed in a DC 17 Strength saving throw being Engulfed by the Colossal Mud Snail on a failure.

Engulf: The Colossal Mud Snail attempts to consume a creature of a smaller size within 5ft of it by moving to its space. it must succeed in a DC 17 Strength saving throw being restrained and drowining in mud on a failure.

A creature restrained in this way may attempt to break free by succeeding in a DC 17 Strength saving throw.

A creature that restrained in this way takes 2d10 bludgeoning damage for each 10ft the Colossal Mud Snail moves.

Furthermore a creature restrained in this way is grappled by the Colossal Mud Snail, and it does not suffer movement penalties by moving when grappling creatures this way.

It can engulf any number of creatures provided they do not ocupy more space than its body.

Stalk Slam: Melee Weapon Attack +9 to hit, 10ft reach, one target, for 4d10+6 bludgeoning damage.

The Colossal Mud Snail can still perform this attack while inside its shell, however it has disadvantage on its attack rolls.

Leave the Shell: The Colossal Mud Snail leaves the shell if inside it.

Shell Armor: As a reaction towards taking damage the Colossal Mud Snail enters its shell.