Shapechanger. The mimic can use its action to polymorph into a Large or Medium land vehicle or back into its true, amorphous form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Adhesive (Object Form Only). The mimic adheres to anything that touches it. A creature adhered to the mimic is also grappled by it (escape DC 14). Ability checks made to escape this grapple have disadvantage.

Drag. When the mimic moves while it has a creature grappled, that creature must make a DC 14 Strength saving throw.  This saving throw counts as an attempt to escape being grappled by the mimic.  On a success, the creature escapes the mimic's grapple and remains in its space.  On a failure, it is knocked prone and dragged behind the mimic for the distance the mimic moves.  The creature take 3 (1d6) slashing damage for every 10 feet it was dragged.

False Appearance (Object Form Only). While the mimic remains motionless, it is indistinguishable from an ordinary vehicle.

Grappler. The mimic has advantage on attack rolls against any creature grappled by it.

Trample. When mimic moves, it can enter a Medium or smaller creature's space. The first time the mimic enters a creature's space on a turn, that creature must succeed on a DC 14 Strength or Dexterity saving throw, taking 18 (4d8) bludgeoning damage and being knocked prone on a failed save, or half as much damage without falling prone on a successful one.

Transport. The mimic can carry up to 1,500 pounds.

Pseudopod. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) piercing damage plus 9 (2d8) acid damage.

Swallow. The mimic makes one bite attack against a Medium or smaller creature it is grappling. If the attack hits, the target takes the bite's damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the mimic, and it takes 14 (4d6) acid damage at the start of each of the mimic's turns.  The mimic can have up to four targets swallowed at a time, not including Tiny creatures.

If the mimic takes 10 damage or more on a single turn from a creature inside it, the mimic must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 5 feet of the mimic. If the mimic dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 5 feet of movement, exiting prone.