Bob the Docile Mimic

Shapechanger. Bob technically can use his action to polymorph into an object or back into his true, amorphous form. But at his age, he really doesn't find it worth the effort, so he just stays in the shape of a chest since it's helpful for you. His statistics are the same in each form. Any equipment he's carrying isn't transformed. He reverts to his true form if he dies.

Adhesive (Object Form Only). Bob can choose to adhere to anything that touches him, but that sounds like a lot of work. If, for some bizarre reason, he does get into combat, a Huge or smaller creature adhered to the Bob is also grappled by him (escape DC 13). Ability checks made to escape this grapple have disadvantage.

False Appearance (Object Form Only). While Bob remains motionless, which preferably is all the time, he is indistinguishable from an ordinary chest.

Grappler. Bob has advantage on attack rolls against any creature grappled by him.

Pseudopod. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 1d6 + 2 bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 1d6 + 2 piercing damage plus 1d6 acid damage.

Old. If Bob finds himself in combat and not engaged, he will always take a Dash action to get the hell out of there.

If Bob finds himself in combat and not engaged, he can--and always will--take an additional Dash bonus action to keep on getting the hell out of there.

If Bob is in combat and not engaged and has a Reaction, he can expend it to take an additional Dash action.