Combat Mimic

Shapechanger. The Combat Mimic can use its bonus action to polymorph into a Small, Medium, or Large creature it has absorbed, or back into its true form. Its statistics, other than its size, 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.

Ambusher. The Combat Mimic has advantage on attack rolls against any creature it has surprised.

Surprise Attack. If the Combat Mimic surprises a creature and hits it with an attack during the first round of combat, the target takes an extra 10 (3d6) damage from the attack.

Battle Form. Once per turn the Combat Mimic may change one of its arms or legs into a weapon that does 2 D8 damage of either slashing, piercing or bludgeoning depending on the form it chooses to shape its limbs into.

Trap Form. The Combat mimic may use its reaction to trap any physical object (including appendages still attached to enemies) that touches it, within its form. somebody wishing to remove themselves or their items from the mimic may make a  DC 15 Strength Saving Throw.

Absorption.  The Combat Mimic may absorb any creature it touches, the creature being absorbed makes a DC 13 Constitution saving throw, On a failed save the creature takes 2D12 Necrotic damage. If the creature has been ensnared by the Combat Mimic's Trap Form it has disadvantage on its Constitution saving throw. If the creature is brought to 0 Hit Points it dies and is absorbed, the Combat Mimic can now take the creature's form. The creature can be resurrected with the appropriate spells (such as True Resurrection or Wish)

Multiattack. The Combat Mimic makes three melee attacks.

Slam. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (2d8) bludgeoning damage.

Slash. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (2d8  slashing damage.

Stab. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (2d8  piercing damage.

Read Thoughts. The Combat Mimic magically reads the surface thoughts of one creature within 60 feet of it. The effect can penetrate barriers, but 3 feet of wood or dirt, 2 feet of stone, 2 inches of metal, or a thin sheet of lead blocks it. While the target is in range, the doppelganger can continue reading its thoughts, as long as the doppelganger's concentration isn't broken (as if concentrating on a spell). While reading the target's mind, the Combat Mimic has advantage on Wisdom (Insight) and Charisma (Deception, Intimidation, and Persuasion) checks against the target.

Trap Form. The Combat mimic may use its reaction to trap any physical object (including appendages still attached to enemies) that touches it, within its form. somebody wishing to remove themselves or their items from the mimic may make a  DC 15 Strength Saving Throw.