Also known as: エコー(ACVI)
An unmanned bipedal AC Mecha in Armored Core VI: Fires Of Rubicon.
Reassembled within <spoiler>ALLMIND's</spoilers> classified simulations, the new designation 'Echo' is without a serial code, though it is made up with parts produced by the Rubicon Research Institute under the serial code IA-C01X 'Ephemera', originally developed for an unmanned AC of same name.
Despite the parts being developed half a century prior, like all Institute developed machines, it is able to keep up and exceed modern weapons in many aspects thanks to it's Coral-powered technology. The AC Echo has an alien but yet feminine appearance, it is painted entirely in black, silver and pink.
<spoilers>Though designed to be unmanned, when it's reassembled into the Echo, it was piloted by Ayre (Armored Core Vi) in the story route 'Alea Iacta Est' to assist the C4-621 in the final mission.</spoilers>