The Atrium is a Biome exclusive to Don't Starve Together, introduced in A New Reign. Its composition is similar to the Labyrinth biome, with some variances. It is isolated from the rest of the Ruins, being only accessible by hopping into a Tentacle Pillar Hole. The Ancient Gateway is located at the end of the Atrium.
The path to the Ancient Gateway looks like a zig-zag, with many Obelisks and Ancient Fences blocking the path. The area is also filled with Dangling Depth Dwellers, Ancient Obelisks and Ornate Chests, much like the Labyrinth.
Like the Ruins, the Atrium has the Nightmare Cycle. Upon inserting an Ancient Key in the Gateway, the Cycle will be locked at it's peak state, and will not leave said state unless the key is removed from the Gateway.
- Bringing The Lazy Explorer and/or a Nightmare Amulet is ideal over manually decreasing and increasing one's sanity in order to pass the Obelisks, since one can easily get stuck or be killed by the Shadow Creatures if they are out of means of doing such.
- An atrium is a name for a room with large ceilings used for worship. The atrium is a play on words with atrium meaning the said room, and atrium, the central chamber of the heart (organ).