Chester (short for Otto von Chesterfield, Esquire) is a unique passive Mob that acts like a mobile Chest. By clicking on Chester, the player can store 9 items inside him. Chester is one of the few Mobs that cannot be frozen.
Chester will spawn once the player finds the Eye Bone and will go wherever the Eye Bone goes. As long as the Eye Bone is in the player's possession, Chester will follow the player. If the Eye Bone is dropped onto the ground or stored somewhere (even inside Chester himself), he will stop following the player and remain in place. Chester regenerates health by 22.5 hp every 3 seconds. If Chester dies, he drops all of the items stored inside, and the Eye Bone will close its eye. If he dies while burning, all dropped flammable items will catch fire and burn to Ash. After Chester dies, he respawns in one game day as normal Chester wherever the Eye Bone happens to be.
Krampus cannot steal from Chester, but Chester can be killed, so he is not a foolproof chest.
Shadow Chester
Shadow Chester is a special transformation for Chester. If he has at least one Nightmare Fuel in each inventory slot on the night of a full moon, he will consume them and transform into a Shadow Chester. Shadow Chester has three more inventory slots than normal Chester or Snow Chester (a total of twelve slots), but if he dies, he'll respawn back as normal. Shadow Chester was the reached stretch goal reward for achieving $25,000 in total pledges in Klei's Chester Plush Kickstarter.
Snow Chester
Snow Chester is another form of Chester. If he has at least one Blue Gem in each inventory slot on the night of a full moon, he will consume them and transform into a Snow Chester. Snow Chester's special ability is preserving perishable items longer, like an Ice Box. Snow Chester was the reached stretch goal for achieving $120,000 in total pledges in Klei's Chester Plush Kickstarter.
Tips
Stacks of Mosquitoes and Killer Bees inside Chester allow him to be turned into a walking bomb that will unleash pain upon death. It's a good idea to drop the eye bone if you plan on doing this; otherwise, you may end up too close to the carnage and suffer terrible consequences.
Lightning can hit Chester. He will be set on fire and run around wildly for a few seconds. Then, the fire will go out. If Chester is at full health at the time of the strike (which, due to his regeneration, he usually is), there's nothing to worry about.
Since Chester regenerates health at a fast rate, he is a useful tool in restoring health. If you attack Chester with the Bat Bat, you will regain health from the hit and have no risk of being attacked by monsters.
It is better to drop the Eye bone on the ground when you are not using Chester to free an inventory slot.
It's better to put the eye bone in your backpack (if you have one) so when you're going to attack you can put your log suit on and drop your backpack without worrying about Chester.