The Sandworm Lair is a second-tier zone on the far western shore of Maj'Eyal.
The Lair consists of small, round, disconnected open rooms. These rooms are the only "stable" parts of the level. Peaceful, invulnerable sandworm tunnelers constantly roam the level, moving from room to room, and leaving trails of unstable temporary tunnels behind them. The mini-map will show stable squares in black (once they are lit) and unstable ones in blue. The player is expected to follow the sandworms to get to the rooms; teleportation is also an option. Entering a tunnel without knowing how recently it has been dug is very risky and not advised. A high light radius and/or some means of illumination is also helpful.
If the player (or anyone) is caught in a tunnel when it loses stability, the tunnel will cave in, burying him in sand. This will do substantial Life damage and will also cause suffocation to begin, for beings which need to breathe.
In addition to the tunnelers, the zone is inhabited by hostile sandworms, jellies, and other monsters. Beware the sand drake's blinding breath and the gravity worm's pinning gravity field. There are also (potentially?) several "glowing chests" on each level, which may contain random artifacts of any tier.
The boss is the Sandworm Queen, a sandworm with summoning (of sandworms) and sand breath talents. Her heart (a guaranteed drop) can be consumed to grant access to the Harmony talent tree (unlocking the tree for Wilder classes who started with the tree locked, or granting the locked tree to classes who did not have it), in addition to 3 stat points, 1 class talent point, and 1 generic talent point.
After returning from the Far East, this zone's backup guardian is a Corrupted Sand Wyrm, on the top level. There will be no tunnelers at this point; they were devoured by the Wyrm. This boss drops a Wyrm Bile potion which gives random stat increases/decreases (-3 to +6 in each of the 6 stats) and a talent category point.
As of version 1.0.3, this zone has an alternate layout. Sometimes, you will find a very large top level with a single gigantic burrowing worm. Follow it, and try not to lag too far behind. Illumination is enormously helpful here.