Mana Rig
The Mana Rig was a complex of structures in Shiv built by the Thran (though at the time of the Thran there was apparently more than one, another being at Halcyon).
It was found by Urza during the events of Urza's Legacy. He managed to get the Goblins and Viashino to work together to operate the Rig. It produced Thran metal for the Skyship Weatherlight as well as a powerstone in which the mana from Serra's Realm would later be stored.
During the Phyrexian Invasion of Dominaria, the Mana Rig came under attack by Phyrexian forces who came to either claim it or, failing that, destroy it. However, to both Yawgmoth's minions and Urza's surprise, the seemingly defenceless structure launched a counterattack by deploying a detachable and mobile segment of itself that could shoot huge geysers of molten lava with deadly accuracy, a feature installed by Jhoira who was in charge of the complex.
This section of the Mana Rig was left behind for Urza to use to continue forging Thran metal and Powerstones while the main part of the Rig along with Jhoira and a large portion of Shiv was phased out by Teferi along with Zhalfir until its return during the Time Spiral storyline.
It's unknown what became of the mobile part of the Mana Rig.
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