A speed run guide on earning the 100 chests opened achievement in Minecraft Dungeons.
MISSION: Desert Temple
This can be done at any point in the game to help boost your power level as there is a good variety of gear to be earned out of these chests. You are only guaranteed 2 chests with this run but as seen in the video extra chests can appear on the path to the room. Once the run has been done, pause and exit to camp and repeat.
Additionally you can check the water ways ahead (2:25 in video) before entering the chest room, the spawn points for them chests are in the water pools on either side.
The camera angle on the chest room shown is the 'lucky' angle allowing you access to the grey superior chest. If the most common angle appears then you will hear the door opening but be unable to enter. This is why you are only guaranteed 2. My personal maximum per run has been 7
HOPE THIS HELPS