The Thoraxe is also an ancient scepter found in The Beetle Lair shaped like an insect's abdomen, the thorax, with a red glow to it. It is seen in the inscriptions of a stone slab, in the hands of a mythical warrior demigod called the Death Knight, once worshipped within the Beetle Lair.
Cyanidium is a poisonous metal that drains the health of a kombatant. The Thoraxe, located in the Beetle Lair, is made of this same metal.
Baraka vs. Mileena
In the Baraka vs. Mileena video in Deception, once the fight was taken to the lower floor of the Beetle Lair, Baraka decided to take matters into his own hands and got out the Thoraxe. However, in Mileena's ending, Baraka was killed despite trying to fight with it (although Baraka's ending revealed it was just another Tarkata and not Baraka himself).