Accustomed to life underground, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in darkness, only shades of gray. You have 4 red eyes.

You are immune to acid damage

You can use your action to polymorph into an object, into your humanoid form, or back into your true amorphous form. Your statistics are the same in each form. Any equipment you are wearing or carrying isn't transformed, it either drops to the floor or is stored within your body, if there is space. You reverts to your true form if taken to 0 hp, or killed. You can shapeshift into any object you have seen before, so long as it fits within a 5’ cube, and not smaller than a 1’ cube. Larger objects are possible, but must be flat. With dimensions within 10’ x 10’ x 2”. Mass is conserved, for example: a 200 lb mimic transformed into a feather pillow still weighs 200 lbs.

Maintaining humanoid form and stretching out limbs is possible, but the resulting loss of strength and stability gives disadvantage to all attack rolls, strength, and dexterity checks made with the stretched limb. Stretching is only possible to 10’.

You are immune to the prone condition while transformed into an object, or in amorphous form.

You adhere to anything that touches you. A Huge or smaller creature adhered to the mimic is also grappled by it (escape DC 8+Proficiency+Strength). Ability checks made to escape this grapple have disadvantage.

While you remains motionless, you are indistinguishable from an ordinary object

You have advantage on attack rolls against any creature grappled by you

Your large, toothy maw is a natural weapon. It deals 1 piercing damage + 1d4 acid damage + strength modifier. As opposed to bludgeoning damage.

A mimics head in humanoid form is just for show. It contains no vital organs. You will not die if decapitated.

Because of your shapeshifting nature, you can move your vital organs out of the way of a lethal strike. When a critical hit is rolled against you the damage is reduced by ½ your level + constitution modifier. Recharges on a short or long rest.