The Swords of Amarnak are two legendary twin blades that have the power to open portals to other dimensions and defeat warriors.
Together, the combined two swords have the ability to open portals to other planets (and, as ZIM states, devastate armies). One sword, however, can conquer individual warriors or small groups of warriors. The Swords of Amarnak were originally created on Petropia (the planet that the female crystal trainee from Hobo 13 is from), whose once grand civilization was fallen victim to the aggressions of the Irkens, and one of them was housed in a temple within that planet while the other one was taken away.
Many centuries later, Zara, an old enemy of ZIM's, wanted the swords for herself and for that she betrayed ZIM and the rest of the Irkens, which led to Zara's banishment.
Years later, Zara reappeared and kidnapped Skoodge forcing ZIM and Gaz to search for the blades. The Tallest and queen found the blade but instead of giving it to Zara, ZIM wanted to fight. Zara was defeated and thrown into the void. The swords were then placed in the armory of the Irken imperial palace for future use by the royal couple.