Randis

Dimensional Ships are vessels, created and operated by the naaru, that can travel between worlds without the use of traditional portals. They are capable of traversing the Twisting Nether just as normal ships traverse the air and sea. Such ships were useful when evacuating important populations from the encroachment of the Burning Legion, such as K'ure's rescue of the draenei. The term usually refers to the draenei capital city, the Exodar — a one time satellite structure of Tempest Keep. More powerful versions of Dimensional Ships are called "Dimensional Fortresses", which applies to the naaru flagship and current headquarters of Kael'thas Sunstrider, Tempest Keep.

A naaru Dimensional Ship in concept art.

The only factual knowledge available is that Tempest Keep has "automated" defenses such as the ability to fly and teleport itself and anything in it by the use of magic in the stead of technology. The automated defenses are most likely more powerful counterparts of the Arcane towers built by the Kirin Tor and the necropoli, such as Naxxramas, that the Scourge employ, which also fly and move vast distances using similar magics.

Notes

• To be clear, we're not talking about having the Millennium Falcon cruising around the Twisting Nether. The draenei 'nether-ship' you've been hearing about is far more than it seems. It's part of a larger dimension-traveling fortress called Tempest Keep that essentially teleports through alternate realities. It doesn’t bank and roll or shoot proton torpedoes (not yet, anyway). - Chris Metzen

• Though Metzen discourages Sci-Fi connections, Dimensional Ships probably work like "hyperdrive" or "slipstream"; that is, the ship enters a sub-spatial dimension (the Nether or alternate dimensions) to traverse space (the Great Dark Beyond) more quickly. Thus, hyper-accelerated space travel occurs from the ships' motion through an alternative dimension. It is then speculated, that when the Exodar crashed it probably materialized in the sky above the Azuremyst Isles and unable to fly in the material dimension, fell to the ground (It is now known that Exodar crashed because it was tampered with by the Blood Elves of Draenor commanded by Kael'thas).

Known Dimensional Ships

• Tempest Keep - Dimensional Fortress
  • The Arcatraz - Dangerous being incarceration
  • The Mechanar - Engineering factory
  • The Botanica - Flora research atrium
  • The Exodar - Unknown (Current sections are themed for Trade, The Holy Light, and Shamanism. Also has a large demon museum.) It is possible that the Exodar was used or was designed to be used as a housing area or general living quarters for the inhabitants, with space for taking care of day-to-day necessities. This would have made it the ideal section to take for the draenei, needing the living space and not knowing the length of time they would be traveling.
• Oshu'gun - Planetary evacuation