Gorgons checkpoint. Hard Mode means you need to wipe before joiners can backtrack to the Exotic Chest. The chest will always be available after you spawn at the checkpoint and backtrack. It gives the same rewards in normal mode. You can only loot a chest once per week per character. Only that one chest has a chance to reward you with an exotic. The other chest in the Vault only reward ascendant materials which are practically worthless. Its the same chest in normal as in hard, you can't loot it twice.

Thanks for the reply! One last question, does the chest ever despawn after a certain amount of time? Or if the fireteam leader is changed to someone who has already gotten it (like the second chest in CE)?