Players who first stumble upon the Underground Passage in Baldur's Gate 3 will likely be using it as a quick way to travel between the Druid Grove and the Goblin territory. After all, that's what the Goblins are using it for. However, there is a treasure here for those who snoop around after taking care of any enemies.
However, the chest is much easier to locate than the key. Plenty of gamers in Baldur's Gate 3 aren't master locksmiths so they'll need the key to open it. It doesn't take a long time but the 
Charred Key that opens the 
Heavy Chest is not located in a place that most players think they can get to.
Updated September 26th, 2023: As players venture through Act I of Baldur's Gate 3, they'll likely eventually come across a slightly hidden area known as the Underground Passage. Inside this area are some enemies to deal with, traps to avoid, and a locked chest to loot. To open the locked chest in the Underground Passage in Baldur's Gate 3, players will need to grab the Charred Key. To showcase how players can find and obtain the Charred Key in Baldur's Gate 3, and open the chest in the Underground Passage, the following guide has been updated with a video.
Getting The Treasure In The Underground Passage
- Disable the Guardian Statues.
- Jump to the middle stalagmite.
- Locate and loot the Dead Human for the Charred Key.
- Jump back to the main area.
- Open the Heavy Chest (from the south entrance, hug the right wall).
The two most pressing concerns are saving Findal and the lethal Guardian Statues. After getting that taken care of, look for the Charred Key on the body of a Dead Human. To get there, jump to the large stalagmite toward the middle of the cave. The body will be at the base of this rock formation.
After hopping back, it's just a matter of looting the Heavy Chest. When entering from the south, hug the right wall and it's impossible to miss. Players who enter on the other side (perhaps those who broke Sazza the Goblin out of her makeshift jail) will find it on the upper level, immediately on the left wall as they climb or take the ramp toward the southern exit.
Baldur's Gate 3 is available in Early Access on PC and will be available on August 3rd, 2023. The PlayStation 5 version will be available on September 6th, 2023. A version for Xbox Series X/S is still in development.