The Muddy chest is a locked chest located in the centre of Lava Maze. It can only be opened with a Muddy key, consuming one key each time the chest is opened.
Opening the Muddy Chest is required in the Medium Wilderness Achievement Diary.
Players attempting to loot this chest should beware of player killers as it is in level 43 Wilderness. If attacked by a PKer, the closest escape routes are descending into the Lava Maze Dungeon or using the stepping stones north of the fenced area (requires 82 Agility and completion of the Hard Wilderness Diary).
Two lesser demons reside near the chest.
At current prices, the loot from one key is worth 3,791 coins, and a net profit of 1,632 coins.
Assuming you have at most 1 other item in your inventory and want to keep all the loot, you can take 6 keys to end up with full inventory of loot. (6*4 + 4 = 28) If you discard/alch the daggers, you can take 8 keys. (8*3 + 4 = 28)