Minecraft Dungeons Lower Temple is a spot located just below the Desert Temple level. Originally, it was meant to be a secret mission, but was cut from the first build of the game—until recently. Now, the level is allegedly being added back into the game with the release of the first Minecraft Dungeons DLC: Jungle Awakens on July 1.
It was meant to be an expansion on the Desert Temple with similar motifs and sandy feel, though significantly dimmer due to the lessened lighting. Legion Gaming has a sneak peek play-through that shows off the level pretty well.
Minecraft Dungeons Lower Temple: Everything You Need to Know
Lower Temple features a more cryptic atmosphere with your primary enemies being skeletal archers and warriors, crypt spiders, and mummies.
According to the Minecraft Wiki, the game loosely describes this place as follows: "Nobody knows how much further down this temple goes. You have to venture deeper into the slumbering catacombs and make sure that there are no lingering Illagers."
Your main objective in this level is to find the golden key that unlocks a second half of the level. Therefore, its likely that more of the Lower Temple will be revealed once the DLC drops. On its own, the current configuration of the level isn't very large—which furthers this theory.
It's unclear just how Lower Temple will fit into the story of Minecraft Dungeons.