From the Super Mario Wiki
Chester is an enemy disguised as a Treasure Chest that appears in Super Mario RPG: Legend of the Seven Stars. Inside the chest is its body, which resembles a tan Ameboid. It is one of the various enemies Magikoopa creates and can be found behind one of the six doors in Bowser's Keep.
Chester is the most powerful member of the Pandorite family, sporting the highest stats in all areas, but also follows a predictable pattern. Its first action in battle is to summon a Bahamutt. On its next turn, Chester will use Sandstorm to damage the entire party, as well as possibly inflict Fear. On its following turn, it will use either Mega Recover to heal or Flame Wall to damage the party. The odds of each is 2/3 in favor of Mega Recover, and 1/3 in favor of Flame Wall. Chester's pattern then restarst. If the previous Bahamutt is defeated, however, it creates another Bahamutt. Otherwise, Chester will use Flame Stone to inflict Fire damage to one character.
As its related enemies, Chester is immune to all elemental attacks and status effects except Jump, which it is weak to.
A friendly Chester can be found on the upper room inside Monstermama's house in Monstro Town. It tells Mario how many invisible chests (or "Surprise Boxes" as it refers to them) that remain yet to be discovered; collecting them all prompts it to say, "Wow, you found them all."
Names in other languages