The Blacklight Barbican is actually two Towers instead of just one. It consists of the 11th and 12th Towers, the Dawn Tower and the Dusk Tower. It cannot be chosen from the Tower menu; it must be entered by either choosing the Dawn Tower or the Dusk Tower. The name itself is only seen on the save menu after defeating the Masters and clearing the Towers. However, the texts found in both the Towers are named "Blacklight: " rather than "Dawn: " in the manner that other Tower texts are named.
Connecting the two Towers which form the Blacklight Barbican are the vortexes which teleport you from one Tower to the same point in the opposite Tower. These vortexes can be activated and deactivated by using the Light stones and Shade stones found throughout the two Towers. Light stones will activate the light portals located in the Dusk Tower while deactivating the dark portals located in the Dawn Tower. Vice versa for the Shade stones.
Because it is actually two Towers, the Master battle actually involves two Masters: one light and one dark. They are counterparts which can only be defeated by using their own attacks against each other. To start the fight, you must destroy 4 chains in both Towers then enter from each door, destroying one of the two center walls each time. A Master will send you back outside if you attempt to fight it before freeing the other. The room in which you fight the Masters of the Blacklight Barbican is also the room from which you access the Centrum, the thirteenth Tower, also known as the "Fulcrum of the Thirteen Towers".
- The first part of the name, Blacklight, clearly comes from the concept of light and dark, or "black" and "light", being merged together. Since it consists of the Light Tower and the Dark Tower which are connected by vortexes, this makes sense. The second part, Barbican, is a Latin derived word which "is a fortified outpost or gateway", "or any tower situated over a gate or bridge which is used for defensive purposes". The Blacklight Barbican is, in a way, preventing anyone entering the Centrum, therefore protecting it.
- It strongly resembles Metroid Prime 2: Echoes, because of the interaction between the two towers is like the Light and Dark Aether from the game. The vortexes act similarly to the portals in MP2.