Box

Lightning Quick. The Box's movements are imperceptible to all sights except truesight, unless it is under the effects of a spell such as Slow. As such, it does not provoke Opportunity Attacks from creatures whom cannot perceive its movements.

Weeping Angel. The Box can't move while being perceived through sights based on eyes, reflections or scrying sensors. Blindsight does not produce this same effect.

Brick. If the Box moves 10ft. in a straight line and hits a creature with a Bash attack, the attack's damage is increased by 1d4.

Bash. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 7 (1d4+5) bludgeoning damage. 

Dodge. Whenever the Box is targeted by a ranged weapon attack, it can make a Dexterity Saving Throw contested by the attacker's attack roll. If it wins the contest, the attack automatically fails. It can't take this reaction more than once per round.

Sneak Attack. Whenever the Box is left unseen, it can move up to half its current speed and make a Bash attack as part of the same reaction, with advantage on the attack roll if the attack targets the last creature to break line of sight with it.