From NewAgeOfPower's homebrew:
About 2 AF, Probe Teams of House Emiya [Argonaut Family] were conducting a survey of small moonlets around the orbit of Saturn. Halfway through their survey, they came across an anomaly, in orbit precisely opposite of the Gatekeeper Corporation's Pandora Gate orbit.
To Radar, Lidar, and Terahertz sensors, there was only empty space in that orbital slot. The most finely tuned gravimetric sensors detected 'something', and while AIs simply logged it as a bug, it kept bugging Anya Emiya (who later became the house head), and so she sent a second expedition. Equipped with Gravimetric sensors, they detected an small asteroid, which proved impermeable to conventional scanning, and attempts to chip away samples proved completely futile.
After years of research, scientists were able to determine that the asteroid was a mundane iron-nickle rock, but coated in an incredibly exotic material. During the first round of testing, this material was determined to be practically indestructible, requiring energy densities of 10^16 GEVs/fermi to destroy. Destroyed volume left behind no residue-
simply vanishing once this energy is attained.
Advanced microscopes determined this material was 'perfectly smooth', even as resolutions approached femto-meter levels. It was quickly dubbed a Femtomaterial.
Asyncs, however, were discovered to able to shape this matter with their abilities, although none have been able to bring it to sub-Planck scale yet. It was discovered to have constant volume; i.e. perfectly incompressible. After scouring the entire asteroid, then carefully breaking it into fine debris, less than 1cm3 of this material was discovered.
This material seems to have no mass, or near-negligible mass, although studies are inconclusive due to the miniscule amount of material available for experimentation. These Async teams named it Ether for its properties.
Manipulation of this exotic matter is very difficult, and this material cannot be deftly manipulated by more than a few Asyncs at a time- interference seems to be an issue.
Micrometer, then Nano-meter, and finally Femto-meter thin sheets were extruded by in-house Asyncs, and yet all sheets proved to be absolutely impermeable to not only EM radiation (until beam density reaches 10^16 GEV Cubic fermi), but also the Strong and Weak Forces, however, Gravity seems to pass through unhindered. It is also frictionless.
Its thermal conductivity properties are unheard of, qualifying as a perfect insulator, and an absolute insulator to electrical/magnetic fields. Atlas Institute [Allied Argonaut Faction] physicists postulate this material is not composed of matter as we know it, at least not Baryonic matter.
Ether cannot be carried through Pandora Gates; in 13 seperate experiments the Ether simply did not appear on the other side; no matter if it was implanted within a synthmorph, biomorph, Faraday Cage, suspended within a Bose-Einstein condensate... After losing 20% of the original volume discovered on the asteroid, House Emiya ceased Ether- Pandora Gate experimentation.
When in the presence of an Psi Jamming field, it resonates with the frequency and becomes completely immune to Async manipulation.
Currently, experiments are in progress to produce absurdly efficient batteries/reactor designs, advanced anti-matter containers, but again, amount of material available is minuscule, and time required for teams of Asyncs to extrude near-Planck thickness material is measured in weeks to months.
A single experimental Katana, edge-to-hamon coated in a sub-femtometer layer of Ether, with the edge measured in Planck lengths, was crafted, and has had a Psi Canceller installed in the handle. It has been shown to even shear through atomic bonds, although the chance of hitting an atom is minuscule.
Needless to say, this blade does not suffer wear and tear.
(Weapon Modifiers: +2D10 + SOM DMG, -SOM AP Melee)
(Armor Modifiers... do you have enough of this to make armor??? Indestructible to anything less than a Particle Collider, or perhaps some serious antimatter pumped weapons...)
[If not exposed to psi jamming/cancelling, Asyncs who succeed a -60 WIL + COG + INT test may reshape this matter according to their knowledge skills. Grok applies here. Psi Cancellers are another homebrew product]
As mind to body, so soul to spirit.
As death to the mortal man, so failure to the immortal.
Such is the price of all ambition.