Shapechanger.
The mimic can use it's action to polymorph into an object or a bonus action to revert back to it's true form. If damaged while polymorphed, the mimic reverts back to it's true form.
False Appearance.
While the mimic remains motionless, it is indistinguishable from an ordinary object.
Grappler.
The mimic has advantage on attack rolls against any creature grappled by it.
Devour.
As an action, the mimic can devour organic material and spawn 1d4 other mimics.
Convert Husk.
As an action, the mimic can merge with a dead corpse and turn into a phantom.
Pseudopod. +5 to hit, reach 5ft, (1d8 + 3) bludgeoning damage.