by aokarasu

Sword of Rupture, Ea (乖離剣・エア, Kairi Ken - Ea) is the most powerful Noble Phantasm contained in the Gate of Babylon and the pinnacle of all those used by Servants. Unlike all of his other nameless weapons that were able to be passed on to other wielders over the course of history, it is a sword only Gilgamesh possesses, a completely unique existence that can only be possessed by him, that is suited only for a ruler's use and makes him transcendent.

It has an abnormal shape that doesn't match what would normally be classified as something specialized like a sword. It is something that was born before the appearance of the concept that the world calls a "sword", so it is not something that can truly be called a sword or have the shape of any known blade. While it has a grip, handguard, and is the same length as a longsword, the section that should contain a blade deviates from the normal form of an edged weapon. The "blade" itself and the tip of the sword, spun in a spiral shape, are dull. It has the shape of a cylindrical, drill-shaped pillar made up of three independently rotating segments engraved with crimson cuneiform lettering that spin slowly in alternating direction like querns, the middle segment spinning clockwise and the top and bottom segments spinning counterclockwise. The drill design was modeled after bedrock excavators used to drill underwater tunnels. While Ea is categorized as a sword, its way of being is closer to a wand. Its three litographs respectively represent the heavens, the earth, and the underworld. It exemplifies the world's way of being by having each one of them rotate in opposite directions. The "cosmos" is thus represented by matching all three of these representations. Everything together represents the universe.

-from TYPE-MOON wiki (http://typemoon.wikia.com/wiki/Ea)