Chester

Magic Resistance. Chester has advantage on saving throws against spells and other magical effects.

Grappler. Chester has advantage on attack rolls against any creature grappled by it.

False Appearance. While Chester remains motionless, it is indistinguishable from an ordinary chest. 

Stomach of Holding. Chester has the same capacity to carry items as a bag of holding, with the following exception. Chester will only give up items it wants to regardless of what it's 'owner' desires. This is at the discretion of the DM. Should Chester be reduced to 0 hp, it will vomit the contents of it's stomach before it dies.

Homicidal Loyalty. Chester will be loyal to whoever has it's bone. It will act independently of its owners wishes, but will do everything in its power to remain within 30 ft. of its owner, including breaking through doors, walls, fortifications and the barriers between planes of existence. It will also fight to protect its adopted owner with a fiery rage.

Fetch. If Chester dies he will come back to whoever holds the eyebone in 3 days. If the eye bone is placed inside Chester he will sit still.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:  8 (1d8 + 3) piercing damage, and the target is grappled (escape DC 16). Until this grapple ends, the target is restrained, and Chester can't bite another target.

Swallow. Chester makes one bite attack against a Medium or smaller target it is grappling. If the attack hits, the target is swallowed, and the grapple ends. The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside Chester, and it takes 7 (2d6) acid damage at the start of each of Chester's turns. Chester can have only one target swallowed at a time. If the Chester dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, exiting prone.

Spit. creature swallowed or grappled  by Chester is thrown up to 30 feet in a direction and knocked prone. If a thrown target strikes a solid surface, the target takes 4 (1d8) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 18 Dexterity saving throw or take the same damage and be knocked prone.