Pocket Dimension

An extraplanar space originally owned by the archmage, which was commandeered by the a**hole vigilantes after his defeat.

Under the archmage's tenancy, the dimension was a single large stone room with an altar on a raised dais, each step of the dais inlaid with small trenches filled with blood, and the altar itself covered in blood.

This plane served as the vigilantes' base of operations for many months during their war for the throne of Atrya. Its garish blood-altar interior was remodeled slightly into a more comfortable atmosphere, and was often used as a safe sequestered place to escape, sleep, or stash items they wanted to keep secure - most notably, the Blood Moon Crystal.

A brain in a jar acts as a physical doorway for the dimension. When placed on the ground and activated, an indefinite portal into the dimension opens, and can be traversed by any number of creatures. This doorway can only be closed by someone on the Material Plane side of the doorway picking up the jar; it cannot be closed from within the dimension.

Not long after the vigilantes successfully seized the throne, Vanessa was disturbed by the brain in a jar, which she kept on her person, vibrating. The party immediately teleported inside to see a surprised-looking elf seize the Blood Moon Crystal and teleport away. This incident threw into question the party's assumption that they and the (deceased) archmage were the only ones with the dimension's coordinates, and the party quickly abandoned it, fearing it to be irredeemably compromised.