Etherium is a magical æther-infused alloy found on Esper. According to the myth, it was created by the sphinx Crucius, and since then most of Esper's inhabitants have parts of their body replaced by etherium. The stocks of etherium are measured in rods. Ultimately the Ethersworn are planning to fuse every living being with this metal.
It is unknown how Crucius made the alloy, even Sharuum could only show how to thin existing etherium. The Seekers of Carmot believe that the substance is made from sangrite and carmot and they possess the Codex Etherium, which supposedly reveals the location of both. However it was revealed by Tezzeret that it was a fraud.
The red substance "sangrite " from which etherium is produced is in fact a mineral that can only be found on Jund, thus explaining why the Esperites cannot craft new etherium. All etherium was originally crafted by Crucius, itself a planeswalker that could obtain sangrite in Jund.
Tezzeret reveals in Test of Metal that he is the Carmot, an essential ingrediant in creating Etherium. Whether he meant him specifically, neo-walkers, Esperites, or human blood remains to be seen.
Carmot was also thought to be a component of the Philosopher's Stone.
|Expansions: Shards of Alara | Conflux | Alara Reborn|
|Shards: Bant | Esper | Grixis | Jund | Naya|
|Characters: Ajani | Elspeth Tirel | Nicol Bolas | Rafiq | Sarkhan Vol | Tezzeret|
|Others: Etherium | Jazal | Kathari | Leotau | Maelstrom|